FUEL INJECTION-MOTRONIC _24a-1 24a Fuel Injection—Motronic General Safety Precautions ........e0eeeseeereee Baa ‘Adaptive Circuitry and On-Board Diagnostics. 240-3 Fault Diagnosis (1993-1995 models) .... 244-3 Basics Requirements . 2 = had Diagnostic Trouble Codes (DTC) . . 24a-5 To display DTCs {models with blink codes) . . 24a-6 To erase DTC memory ..... 2haS Fuel Pressure Tests (1993-1989 models) 242-9 To check system line pressure .....+++++++ 24a To check residual pressure... . 24at0 Electrical Checks and Component Testing (1993-1995 models)............ 24a-10 Power Supply Components Bhatt To test power supply relay (J16 or J271) ... 24a-11 To test oxygen sensor heater relay (J208 oF J276). «06.06. .++ 24at2 Engine Coolant Temperature (ECT) Sensor (G62) .-...-.++.. = Bhat5 Engine Speed (RPM) Sensor (G28) .......24a-21 Intake Air Temperature (IAT) Sensor (@72). .24a-21 Component Replacement (1983-1995 models) ..............6....24a-22 To remove and install Motronic Engine Control Module (ECM)... .66000.0.22. 240-22 To remove Engine Coolant ‘Temperatura (ECT) sensor . To remove Throttle Position (TP) sensor. To remove Mass Air Flow (MAF) sensor . To remove fuel injectors. .. To remove fuel pressure regulator. ....... To remove Idle Air Control (IAC) valve To remove throttle valve housing. To adjust throttle dashpot (cars with manual transmission) . On Board Diagnostics Il (1996-1999 models)....... ‘©BD II component locations (AAA engine, 1996-1989 models)... ‘Throttle Position (TP) Sensor (G69)....... 244-18 OBD II component locations Mass Air Flow (MAF) Sensor (70) ....... 244-17 (ABA engine, 1996-1999 models). ‘To check mass airflow (MAF) sensor Readiness codes vottage and ground... +++ -24at7 To check readiness codes. Fuel Injectors .. :2hat7 To set readiness codes .. To test fuel injectors 2hat8 Oxygen Sensor (G39). 2hat8 TABLES To test oxygen sonsor. .. = 24a-19 a. Motronic Diagnostic Trouble Codes Idle Air Control (IAC) System ............ 242419 (Blink Codes) 1983-1995 model years... ...24a-7 To test IAC system... | 24-20 —b, Fuol System Line Pressure ...... +... .24a10 Camshaft Poston (CMP) ‘Sensor (G40)... 24-20. Residual Fuel Pressure (after ten minutes) 242-10 To test CMP sensor . + 2ha-20 — d. Motronic ECM Electrical Tests... .. Bhat? GENERAL Fuel Injection Systom Applications This repair group covers Bosch Motericfuslinjodioncom- 7 AOC Bite - g Meng ionants ponent troubleshooting and repalt for the 1993-1999 2.0 liter “ABBE Ren) ABA engine and the 1994-1999 2.8 liter AAA (VR6) engine. 1983-1995 models . . Motronic M2.9 ‘Special esting equipment may be necessary for some ofthe 1996-1999 models Motronic M5.9 tosis and repair procedures given here. + AMA 2.8 ter) 1093-1095 models «Motronic M2.9 Nore — 1996-1998 models * Motronic ME. 1886-1968 ABA and AAA engines ere equipped wth + AAZ (1.9 iter) 1 Diet Fuel incon Mone M9 (08D 1. ki recanmended Pat aut ce +AHU (Hite... « Digsel TD! grote and toubkehootng be carted ot usig he Speatl Volewagen scan tol (VAG 1551), 0 an apero- CENERAL piato ‘ganorc" scan tot, PLE)5 24a-2 FUEL INJECTION-MOTRONIC NoTE— + Fuelpump and fuel tank testing and repair information ‘is covered in 20 Fuel Storage and Supply. + Emission systems, such as Evaporative (EVAP) emis- sions, and Exhaust Gas Recirculation (EGA) are cov- ‘red separately In 26 Exhaust SystomvEmiesion Controls. + Knock sensor testing and repair information is cov- ‘red in 28a Ignition System-Gasoline, Fig. 1 shows a schematic view of the Bosch Motronic en- gine management system. The Motronic system combines the ignition and fuel functions into one system, managed by a ‘single engine control module (ECM). The systamis fully adap- tive and features builtin diagnostics that detect and store cod- ed fault information. There are no basic adjustments or settings that can be made to the system. NOTE— ‘A ganoral descristion of operation for the Motronic en- ‘gine management stem is given in 2 General Infor- ‘ation. | line. Prolonged contact with fue! can causa finess- WARNING — Fual wil be alscharged during many fue! s¥stom {est procedures. Do not smoke or work near heaters oF other fre hazards. Have a fre extinguisher handy. Work only in a wollventlated area. Wear suftable hand protection when working with gaso- 8 and skin alordrs. ‘CAUTION— + Connect and atsconnect wires and test equip- ‘ment only with th ignition off + Bolore making any electrical tests that require ‘the angina to be cranked using the starter, ds ‘ble th igntion system as described in 28a kar nition Syster--Gasoline. + Alvays walt at last 40 seconds after turing of ig- ‘niton betore removing the ECM connector I the ‘connector Is removed betoe this tne, residual ‘Power inthe system olay may damage the ECM. + Cleantiness 1s essential when working on the uel system. Thoroughly clean fuel ine conneo: ‘tons and surrcundlng aroas botora loosoning. Avoid the use of compressed ai, ancavoid mov- Safety Precautions ing the cat. Only instal clean parts. “Tho following warnings and cautions should be adhered to i whenever doing work on the fuel injection system. - ————— ecoracen @ nemo Someencat— | ast strate pa ‘neon toa 4 ati Bemasien, | | comes T reas opine \ a ray Saati ~ 4 ‘tomo ort) Srgorvorare (eo ce) aes barns Sam 1" = a ecm \ nee es a wera ; oe Fig. 1. Schematic view of Motronic engine management systam. GENERALAdaptive Circuitry and On-Board Diagnostics (OBD) “The Motronic systemis adaptive. idle speed, ignition timing, injection timing and quantity automatically compensate for ‘and adapt to changos in the engine due to wear or small prob tems, such as minor vacuum leaks. AS a result, idle speed, fuel mixture (%CO) and ignition timing are non-adjustable. NoTe— + Volkswagen identities electrical compononts by a let fer and/or & number in the electrical schematics. See 87 Wiring Diagrams, Fuses and Relays. These ‘alectcal Montrs are sted as an aid to electrical troubleshooting. ‘The Vokswagen Scan Tool VAG. 1851 ie used to ‘quially acesss the Disgnostic Trouble Codes (DTCs) through the data fnk connacior(s) in the dash, Alter- atively, the data Ink connectors) can be Jumpered ‘and the DTC can be read out through the Check En- ‘ine light, also called the Malfunction Indicator Lamp (IL), in the form ofa Blink code. + Baginning in 1984 (1988 In Calllorna), automakers are required by law to apply uniform terminology, ‘words and terms for certain components. Thase stan dardized forms wil be used throughout this section. FUEL INJECTION-MOTRONIC 244-3 ‘The Motronic system features built-in diagnostic clrcultry to detect and store Diagnostic Trouble Code (DTC) information. When the system compensates for values that are outside the Permitted limits, @ fault code is generated and stored in the ECM's permanent memory. For emissions-relatod faults, the Check Engine or Matfunction Indicator Lamp (MIL) will be tumed on. The fault codes can be accessed through the data link connector(s) in the dashboard. FAULT DIAGNOSIS (1993-1995 models) Fig. 2 shows Motronic component locations for the 1993- 1995 AAA (VR6) engine. Fig. 3 shows Motronic component locations for the 1993-1995 ABA (4-cylinder) engine. Because the lgntion, fuel injection, and emission control functions are inter-related and controlled together by the Motronic engine management system, iti dficutt, if not im possible to isolate general driveabilty problems by examining Components ofthe fuel injection system alone. For this reason, the first step in looating trouble Is to review thebasic requirements ist shown below. Hnofaults are found, continue by checking for Diagnostic Trouble Codes (DTCs), especialy ifthe check engine lights laminated. © Brasneeaaeaayre nse 2. nearer 4. Not applicable to vehloles covered bby tile manual 5. Knock sensor 1 (G61) + $88 28 Ignition System for roparifermation 6. Motronic engine control module (ECM) (1220) 7. Throttle valve housing 8 Throttle position (TF) sensor (G9) Idle alr control (IAC) valve (N71) Not to vehicles covered by thle manual Ignition colt (152) AIG thermal switch (F45) Engine coolant temperature (ECT) sensor (@62) * blue, 2-pin connector Afenrun cotat fn conto thermal ti Fy ‘coolant tempersture sensor for temp. gauge *yelow, 4-pin connector 15, Intake sir temperature (MAT) sensor (G72) 16. Fuel pressure regulator 117, Engine speed sensor (G28) 18, Knock sensor 2 (G68) + 50028 Ignition System for ropa informstion 19, Fuel Injector, cyl no-1 (N30) 20. Evaporative (EVAP) emission canister 21. Alrcloaner (ACL) 2 123 46 6789 01 T t 2019 18 17 «1615 141312 +2. Motrerlo comparant ovation on 1963-1006 AAA (VR6) engines. wave FAULT DIAGNOSIS (1993-1995 models)h 24a-4 FUEL INJECTION-MOTRONIC Basic Requirements Below are a fow basic checks thet should be made if the Mattunction Indicator Lamp (MIL) I-netiluminated, but en- gine management driveability problems are encountered. 1, Check intake system for leaks. Check for cracked, loose, ‘or disconnected hoses and duct work. Check thet all hose clamps are tight. Check small vacuum hoses, especially ‘lose to the ftings, and check the fitings themselves. NoTe— ‘An irleak atows unmeasured arto onterthe engine, of- ton resulting In an overly lean fuel midure, This can cause civeabilty problems and may lumina te MIL. 2. On 4-cyiinder engines, check the intake air boot ‘mass alr flow (MAF) sensor for excessive oll deposits It heavy deposits are found and the engine Is experi encing driveability problems, the MAF sensor ma contaminated. Test the air flow sensor as described wf erin this section. + Barpopeguaeas 2 Sonat ga hina) sean Salter saa Wie 2 tal yl non eon ra 4 Meo tow A soa) 4 ete poaton ser 6) 5. Motronic engine control module (Eom (220) 5. Oxygen sensor (636) hamess 7 Mie ai temperature (AT) sonsor 8. ear contol 1AC) vave (N74) " ©. EGR tamporstue sensor (G38) “seo 26 Exhaust Systenvemlesion Kt ‘Controls orreparinornason 10. EGR valve “se 26 Exhaust Syston/Emiosion Controle or ropayinrmaton 11. comp tube “not srpeale onal onginae 12 orton atten) eee 28 Ignition System fr repcir ‘ermal 18, Vocle speed senor (¥88) (422) we rare . nan soln epee (ET ‘Seneor fortemp- gauge ( “Biase pin connector 15. Central mess connector 16. Knock sonsor (G61) harness con- ester 47. Engine speed sensor (@ Ratese Soonsser™ 2) 18. Engine speed sensor (628) 18, Ignition ditibuter with camshaft onto sonar (Gio) ‘mtn "ere 20. Fuel pressure mensuring top ~not appeable onal engines 23456 26 25 24 23 22 21 2019 y 21. Fuel injectors (430-N33) 22, Knock sensor 1 (G61) + repairing, 98 28 ignition System 23. Ground connection 7 pp pape 18 17 1615 14 2. Fuel pressure regulator 25. Thermal vacuum valve (TVV) + forintake airpreheating 26. EVAP canister a * located below air cleaner Fig. 8. Motronic commonentiocstion on 1963-1995 ABA (C-oytiner engine, FAULT DIAGNOSIS (1993-1995 models)3. Check that the battery is in good condition. Check that the cables are tight and free of corrosion. Gheck that all related ground points are firmly connected and in good condition, 4, Check all of the harness connectors for damage and corrosion, especially the connector at the speed sensor (G28), the main 28-pin connector at the rear ofthe en- gine, ‘and the knock sensor mounts on the engine Block. Nove — ‘4eyliner engines use one knock sensor. 6-ylinder ‘engines use two knock sensors, one on either sido of the engine.” 5. Ifthe engine won't star, check for power and ground at the Motronic ECM, See 97 Wiring Diagrams, Fuses ‘and Relays, Check the fuses. 6. Mako sure there is fuel in the tank and fuse no. 22 Is OK, 7. As the final step, check for Diagnostic Trouble Codes (OTC) as described below. Diagnostic Trouble Codes (DTC) ‘The Motronic systems are equipped with builtin faut diag Nostios. Some of the faults will luminate the chock engin light, but many will not. (On 1988-1895 models diagnostic rouble codes (DTC) can be displayed in one of two ways; (1) using the specialized Volkswagen scan too! V.A.G. 1551 or (2) by jumpering the data ink connector(s) and interpreting bink codes through the malfunction indicator ight (MIL) in the instument cluster. The procedure below describes the blink code method. ‘On 1996 and later models the diagnostic trouble codes (DTC) can only be displayed by using the specialized Votk- ‘swagen scan tool V.A.G. 1651. DTCs are accessed through the data ink connector(s). The connectors are behind a cover nthe center of the dash, below the heating ventlation controls. Two versions of data link con- noctors are used depending on model year. 1993 and early 1834 care use two connectors while later model 1994 and lt- cercars.use a single connector. See Fig. 4. NoTE— (On 1996 cars, a spectal OBD adapter miy be stored ‘beneath tho rear seat and shouldbe used to acouss tho DTCs. See Fig. 6. On cars with ABS, the connactor is stored beneath the ABS coaxial cable next to the ABS contol unit. On cars without ABS, the adepter Is se- cured by a wir te. Fue INJECTION-MOTRONIC 24a-5 0s Nowco08 Fig. 4. Data tk connectors In conte of dash, 1208 ane ently 1904 (top cars use two separate connectors Later model 199 (bot ‘om) and later cars use single 16-pn connector. Special VW scan fo0lVAG. 1551 shown, Fig.5. 08D adapter uaed to aooe0s blink codes on Inter 1994 and +1995 model yaar vehicies. On some 1995 vehicles, adapter may be attached to the wing harness under the rear seat FAULT DIAGNOSIS (1993-1995 models)24a-6 FUEL INJECTION-MOTRONIC To display DTCs (models with blink codes) 41. With the ignition key in the on position, jumper the ter- ‘minals in the data link connector that match the vehicle configuration. See Fig. 6. * On 1999 and early 1994 vehicles, jumper position 1 Inthe black plug to postion 1 in the white plug with a sutable jumper wire. This connects the biink code activation signal wire (white plug, position 1) to a ‘ground (black plug, position 1) to initiate the blink signal, The jumper should be connected for about 2-112 seconds and then removed. * On later 1994 and 1995 vehicies, jumper position 4 of the 16 pin data link connector to postion 15 of the data link connector with a suitable jumper wire or adapter. This connects the blink code activation signal wire to a ground to initiate the blink signal. The jumper should be connected for about 2-1/2 seconds and then removed. ‘CAUTION— Use care when connecting the jumper wire. Posi ‘ive (+) battoryvotiage s present in the connector. ‘Awrong connaction can result in damage to ECM cor the vehicle’ wing. Ae Ashe rs ani2y ian 1994 , ® r 1 ° Ao later 1994 ba i and 1995 Fig. 6. Jumper wie inetalled In data nk connector. FAULT DIAGNOSIS (1993-1995 models) 2. After one blink of the MIL light, the first 4-diit DTC wi bbe displayed. Approximately one second later, the MIL. ‘wil bink the first dig then pause, blink the second di it, then pause, and so on. Table a lists DTCs. NoTE— A Blok code of 2-1-1 will aways be cfsplayed be- ‘cause the ECM only reads the engine speed (RPM) ‘Sensor signal when the engine Is running. This code ~~, vl erase sof once the engine is started. 3. Once the first DTC has been displayed, reconnect the. Jumper wire or the adapter for 2.5 seconds and th, remove it.The Second DTC code (i present) willbe dis Played. NOTE— Fecord blink codes on paper for later reference. tan ‘error is made reading Bink codes, they can be recalled ‘a3 many times 28 needed as fong as they have not been erased. ‘4, Repeat step 3 unt no more codes are displayed. NOTE— End of Bink code display wit bo identiied by 4 long blinks (0-000), 5. When all codes have been displayed and record. ‘tur the ignition key off.FUEL INJECTION-MOTRONIG 248-7 Table a. Motronic Diagnostic Trouble Codes (Blink Codes) 1993-1995 model years armen oo ry ‘No BTC recognized No corrective action necsssay, _ 1281 ‘Vehicle epoed sensor (VSS) (G22) orincorrect |” Check output signal the from spaedometor VE ga Seo Bae fant Englne speed (RPW) sensor (G28)-misingcrinconectspm | Check he wiing andthe rlace thew senor Sigal hace ape boprson let eran | Chea ernest waa Taunteé andthe Sensor rea ita eetegeaes e | hg tore ee oneness | Set Sat Wetec | meee | Emin tate waraiaoe ‘Incorrect signal from sensor, CMP wiring damaged/open or shorted, CMP (Hall) seneor faulty, | Chock th wiring and signal tom ofthe CMP (Hall sensor. On ‘4oylinder engines, check that the dlstbutar is comecty, | installed. On 6-cyinder engines, chock thatthe sensor Seoul mounted tthe cylinder hea Test the signal om tho Hall sensor. Check camshatvvalve timing. Bia ‘Throttle position (TP) sensor (G89)-missing or incorrect | Signal fom TP sensor, TP sensor wing damagedopon or shorted, TP sersorfaily, (Check the wiring and signal trom the TP sensor, Ear} Engh coolant iemperue (ECT) sensor (@62,- ning br React strat fom CT eanor cCT nena oe (Check the wiring and signal rom the ECT sensor. Check for | ‘corrosion a the connecor, causing Interment (eporadle) shor EST coor aay franneter, 2142 | Kg sensor (8) 1(G81)-iasna moored eqnalfom | Oheck ie wena ard sana Fon krack sand Ghoaho frockoonar to EOM iret conscraines OF | toro oe mounng batts fe eck Shes ecre shored nook woneo tye sencor mong eat 600” | Senn sonearemt tae Hock. Chace coreion | feat ante und, the CoM maybe aus Bisa | Knok sensor) 86) (yinde engin nip mang] Check ie wng ancl ram tnocksamser Thode x noonect tral Fo knock sorer@ ECM, oak soaat”| Sau eb mening oe lok Gea ee wna davagelonen or sor, koak conor taal or | basen sont and enence Res ene sen Sonor mouting Pot iose CGN ao Tee ey be fag | #2 | Hetied ome sensor (aire ngge snsor dala | Checkibe angen sone aun aga age aay Ech: Somer hater cat may boob ake Betwean an oH) Choc nen Sova nae a 2412 Intake alr temperature (AT) sensor (G72) — missing or | hook the wing and Signal fom the aT sensor =| Iaroa sgn rom At ser a oes wn Saragodpon sored, AT const ooh 2231 Baia vote inane jton valge (ow 10 vats o | Cheahe charging arn, Date comasione ain over iB vokewih argent) roots 223t {lear control (AC)—sal-compensating idle draitproblem | Check the IAG valve (dy, sticking, Binding) Check ora | rent te speed rele mitra to lean ortoo ren). | lak betwean MAF eae and wigke Maree ora EA | ve operon. | 2141 gok sensor (KS) | (G61) Control— fauly knock sensor | Check the knock sonsor (see DTO 2142 above. Iino Tauns Conalinneron Roa an bo fond ECM pobaby aay moderns | | Feplaced. 2361 | Oxygen sensor contro} Incorrect oxygen sensor signal to | Check the oxygen ‘senor heater lrcult and sensor output | ECM (elmo oc an orto tal). Soneorhoster cut. | iid We eee ono ee ene eo nay pon a ay alae conan and exhaust mel ches oes ine rpms en ete eb) eck gniton seam br moos crenttie eat Nigh), check for leaking or stuck open fuel injectors, check the aprav (EVAR) aries on yer (ure epuar ve ack oper) 2d | Warimum anal speed i ine verveved | Choke engine sped sensor wing ion ra (noose! donna or ala Wom ongne sooes cal froorea Bat4 Fngine-totransmiesion electrical connection wire | Check the wire balween Motonio EGM [pin 18) and ‘shorted te ground (cars with automatic transmission. ‘anomission contol module (TCM) (pin 8). (continued on next page) FAULT DIAGNOSIS (1999-1995 modes)L A i 24a-8 FUEL INJECTION-MOTRONIC Table a. Motronic Diagnostic Trouble Codes (Blink Codes) 1993-1995 model years (continued) DTC | Probable aut Corrective action, fst check f 2243 | Fuel consurmption elgnal signal wie fom ECM to ‘Check wire between ECM (pin 5) and netument castor | instrument cluster shorted to batey postive (B1). (Connector Te) " - | 2304 Mass air flow (MAF) sensor (G70)-MAF sensor faulty, ‘Check the MAF sensor connections and wiring. Check for ~ missing or incorec signal, MAF sonsor wing damaged/open | intake alr leaks. On VR6 engines, chock or eansor burtoft (oF shorod. Largo Inaka lake On deinder 2419 | Mixture control adjustment-fuel mnture to ean ortoo rich. | ‘Check or conditions causing oh or lean runing condilors {S00 DTC 2342 and 2204, 2941). Check he oxygen sensor — heater cicutt Chock the EVAP caistor purge regulator va (ways open). ‘ } 2a LEGA temperature sensor (@08)-faulty sensor or sensorwire | Check the wiring and resistance of EGR temperature sensor — shorted fo ground ms ) ‘3494 | Hosted Oxygen Seneor Relay (J278}-heaierlayicrout | Check the oxygen sonaor halo Grau | matiunesoning (6cyinder engines) ‘811 | Secondary ar Injection solenoid relay (N290)-faulty olay | Check the wing t fay. Check tion of lay, ‘or wiring f relay damaged/open or shorted. mie wae ats ‘Secondary ar injection solenoid valve (N112}tauly valve | Check the wiring o valve, Check function of solenoid valve, ~~ 0 wing fo valve damagediopon ar shorted. 4832 ECM final output stage-fauity ECM or mechanical auld | Checkshe wing and sta ouput component unions (AC loose connections 19 EOM auiput components, ‘aN, tel injectors, EVAP canister purge regulator valve, ‘orion col, tol pup) no faults ean be found, tha ECM A, probably fay ahd shoule be replaced, 4042 | EVAP canister purge regulator valve (NBO}-fauty valve or | Chock the wiring o valve. Check tunaon of solenoid valve. = \Wisng to valve demagedopen or shorted. "a “ ait Fuel injector no. 1 (N20)-injector faulty or wring to valve | Check he witng o valve, Check jorinjecior egal using LED | amagediopen or shorted. ‘estlight or injector signal tester. elgnals present, jects} probably feuty and shouldbe replaoad. ‘4412, | Fuel injector no. 2 (831)-injoctor faulty 0 wiring to vave | Seo DTG 4411, ~ damagediopen oF shored, J | 413 Fuel injector no. 3 (N32)-injector faulty or wirng to valve | See DTC 4411 Ne sdamagedopen oF shorted. | | 4414 | Fuel injector no. 4 (Naa}-njctor fay ar wring to valve | See DTC iti, = damagedonen or shortod. y aunt Fuel injector no. & (NB3)-injoctor faulty or wiringio valve | See DTC 4att. ~ ddamagediopen or shorted. ae Fuel injector no. 6 (NSa) injector fauly or wing tovalve | Seo DTC 4417, ~T | samagediopen 0: shorted - ast ‘dle air control (IAC) Valve (N71)- faulty IAC valve or wiring | Check the IAC vaive (dirty, sticking, binding). Cheok for air [Svat damagedopen or sore. Ieakbetwoun MAF sont and aia marl Ghece EGR valve operation. L “4433 | Fuel pump telay (J17}-reiay not operating or wiring shorted | Check te rolay wiring. Test relay circa. see 20 Fuel Storage. | te batery postive (2) [a8 Supply. “12 | EGR vacuum regulstor solenoid valve (N18)-fauty valve | hook the wiring to valve. Chock funcion of solencid valve, ‘or wing to valve Gamageclopon or shorted. ) 7177 | Motronic engine control module (ECM) (3220) ECM Tauly | Wno othe faut can bo ound, the ECM is probably fauly and {cecroic component alurein EM). shouldbe replaced, ie J FAULT DIAGNOSIS (1993-1995 models)To erase DTC memory 1. Connect appropriate jumper or adapter to the DLG as Previously described. 2. Switch ignition on, but do not start engino. NOTE— Fuel punp wil switch on without engine running. 3, Leave jumper or adapter connected for at least 5 sec ‘onds and then disconnect, 4, Reconnect jumper or adapter for 2.5 seconds and then disconnect. 65. The first bink code will be displayed, 6. Repeat step 4 to display all blink codes stored in me- ‘emery until 4 long blinks;(0-0-0-0) are alsplayed. Nore— All bink codes must be displayed botor they can be cased. 7. Reconnect jumper wire or adapter for 2.5 seconds and remove it.The DTC memory is now erased, 8. Switch the ignition oft, nore— ‘Confirm thatthe memory has been arasod by cisplay- ing blink codes. Only bink code 2-1-1 shout be de played. FUEL PRESSURE TESTS (1993-1999 models) ‘Checking the fuel pressure is a fundamental part of trouble- ‘shooting and diagnosing the Motronic system. Fuel pressure has adirect effecton fuel mixture and driveability, An accurate {uel pressure gauge witha range of at least 0 to 5 bar (approx- ‘mately 0 to 100 psi) will be needed to make the tosts. Fig. 7 ‘shows the connection ofthe fuel gauge, ‘There are two significant fuel pressure values: 1) System pressure—reated by the main fuel pump and regulated by the fuel pressure regulator, and 2) Residual preasure—the pressure maintained in the closed system after the engine Is shutoff. Before making the tests described below, make sure the ‘ul pump is operating correctly and that the fuel pump dliv- cry rato Is within the acceptable timit. Seo 20 Fuel Storage ‘and Supply. __FUEL INJECTION-MOTRONIC _24a-9 Warning = Fuel Wil be cschersed when dconnecting to! fs. Bo not smoke oF Work nea eaters Oty fiw hazard. Have af extguster han Werk ony ha wol-vrtated are. Bove ual promors bn te Ine (as desorbed eater wap'a ace around the ne blero cormesing. NoTe— ‘Some late model cars with the ABA (2.0 Iter) engin ‘are not equipped wit @ fuel ral test port. On these cars, deconnect the fuel supply ne and connect the ‘gauge (using a T-Ating) between the fuel mail and the ‘supply fine. To check system line pressure 1. Relieve the fuel pressure in the system and connect a fuel pressure gauge as shown In Fig. 7 \ VAG 131 ‘2105, na 018 Fig. 7. Fus{pressure gauge instalation on ABA enghns top) and AMA ‘engine foottom). Remove the cap sorew from the test port ‘and connect the gauge tne, FUEL PRESSURE TESTS (1993-1999 models)| 24a-10 FUEL INJECTION-MOTRONIC_ 2, Start the engine and lett idle. See Table b for fuel pres- sure specifications. ‘NOTE — It the engine does not start, run the fuel pump by by passing the fuel pump relay as described in 20 Fuel Storage and Supply. 3. With tha engine faling, disconnect the small vacuum hhose from the fuel pressure regulator (FPR) and check that the fuel pressure increases as spectiod. ‘Table b. Fuel System Line Pressure Engine Fuel Pressure ‘ABA engine (0 et) ‘vacuum hose @ FPR connected 2.5 bar (96 pl) ‘vacuum hose @ FPR disconnected 8.0 bar (43 pa) "AKA angina (28 ler) 1 ‘vaovum hose @ FPR connocted 9.5 bar (51 ps) Yaovumhose @ FPRaeoonected | 4.0 bar (638) Hf systam pressure Is too high, first check for a blocked or damaged fuel retur line from the pressure regulator. Also ‘chock the retum lino check valve on ABA ongines. i there aro ‘no obstructions, replace the pressure regulator. it system pressure is too low, frst check for fuel leaks. Test ‘uel pump delivery as described in 20 Fuel Storage and Sup- ply. A restricted fuel filter or a damaged fuel line are aiso po- tential causes. If there are no other faults, replace the Pressure regulator. Nore— _Addfitional tuet pump tests, including testing the fue! pump ‘olay, are covered n20 Fuel Storage and Supply. To check residual pressure Hotstar problams are usually the only reason to suspect residual pressure problem, but it deserves a routine check as long as the gauge is connected. 1. Rellave the fuel pressure in the system and connect a fuel pressure gauge as shown earlier in Fig. 7. 2. Fun the engine for about 30 seconds to pressurize the system. 8. Tum the engine off, 4. AMter ton minutes, observe the pressure gauge. See Table c. Engine Fool Pressure ‘ABA engine (2.0 ter) AAK engine (2.8 tar) 2.0 bar (29 pa) 2.5 bar (80 pal) Iv the pressure drops beyond specification, check for leaks. in the fuel fines, at the fuel pump, and at the fuel injectors. there are no leaks, ether the pressure regulator or the fuer pump check valve is faulty. 7 To determine which, run the engine briefly to build pres—- ‘sure. Shut the engine otf and immediately clamp shut the fuel retum line atthe pressure regulator. pressura still drops, the fuel pump check valve is fauly. See 20 Fuel Storage an Supply tor fuol pump replacement. fresidual pressure is now OK, the pressure regulator is faulty a ELECTRICAL CHECKS AND COMPONENT. TESTING (1993-1995 models) “The electrical tosts under this heading will holp 1 locat~ electrical component falluro. Unless a spacticdiagnostic rou. ble code (DTC) has been recorded, make the ECM pin-out tost first as listed In Table d. The checks listed In the table~ check the components and wiring to the components. ‘The ECMis mounted in he rear of the engine compartment, ‘With the ignition off for atleast a minute, unplug the connect from the ECM. See Fig. 8. Terminals are marked on the ness connector. ‘CAUTION + Use a high-qualty digtal automotive mttmetor to mako tho tests, An analog (swing-needle) ‘mater should not bo used as ican permanenty ‘damage electronic camponents. + Always connect and dlsconnect the ECM con- ‘nector and moter probes withthe ignition off to ‘avoid damage to electronic components. Wait at least 40 seconds after turing of the ignition be- - fore removing the ECM connector. ) References to Motronic components and their connector _ {terminals are used throughout the table. Use the appropriat ‘wiring diagram to identiy those terminals. See 97 Wiring Dies” grams, Fuses and Relays. ‘When making tests at harness connectors, probe from th. roar of tho connector only 1o avoid damaging the small con- necior terminals. Separate the connector housing and re- move any seals to gain aocess tothe wiringin the connector.) ELECTRICAL CHECKS AND COMPONENT TESTING (1999-1996 mods)Fig. 8, Motronic ECM in rear of engine compartment jarrow). Sopa ‘ate harness connector snd rake connections fom rear of connector. Before making any electrical checks or tests, make sure the following conditions are met: Requirements: altery positive (+) voltage OK + Fuse no. 18 (and no. 21 on AAA engines) OK + Ground connections on engine and transmission OK, es- pecially the connections at the ground bus below the in- ‘take manifold + Fuel pump and uel pump relay OK. See 20 Fuel Supply and Storage. Fig. 9. Power supply oomonents, To test power supply relay (J16 or J271) 1. Working at the fuse/relay panel, remove the power sup- ply relay. See Fig. 10, 19 || 20 || 21 || 22 || 23 || 24 13 || 14 || 16 || 16 |) 17 || 18 Power Supply Components ‘The Motronic engine management system relies on three relays for proper operation; the power supply relay, the oxy- {gen sensor heater relay, and the fuel pump relay. Soe Fig. 9. All three relays are energized (grounded) by the Motronic ECM. The power supply relay supplies power to the ECM and. many of the Motronic components when the engine is run- ring. this relays faulty, the engine will not start. The oxygen ‘sensor heater relay supplies positive (+) voltage tothe oxygen. ‘sensor heating element to heat the sensor. The fuel pump re- lay supplies powerto the fuel pump. A basic check of these re- lays is given in Tabled. NoTE— Fuel pump electric! tests are covered in 20 Fuel Stor- ‘age and Supply. V7 || 8 || 9 |[fo]fa1 ‘tte eeeaiaaeeezesanal | LRREAAKERAHE ARASH ca) Fig. 10. Motronic powor suppl relay in fuse/relay pane! (pesition 12). 2. Check for constant (+) battery voltage at relay terminal 30 in the fusarrelay panel . Reinstall the relay and check that the relay olioks each ‘ime the ignition key is turned on. ELECTRICAL CHECKS AND COMPONENT TESTING (1999-1995 models}; e A 24a-12 FUEL INJECTION-MOTRONIC . f —__ | 41 as tard dcorat be tarascomes: 1. sig betel rg, crete it tor from tho Motronic ECM and separate the connector {gen sensor harness connector. housing. Reconnect the connector to the ECM. - i 2. Connect a voltmeter between the rediwhite wire and : 5. Check for ground at ECM terminal 8 each time the the brown or brownited wire in the connector. The” ignition is switched on. should be battery votage with the engine running. F + If ground is not preset, check the witing between ‘cornoct tne connect: ‘olay terminal 85 in the fusotrelay panel and terminal + H'voltage is present, the relay is working correty. “~ ; 9 in the ECM connector (blackforown wire). no + voltage is net present continue testing. ‘ wiring feults are found, the ECM is most kal faulty. i 3, Working above the main fuse‘relay panel, remove the. ; 6, Check for positive (+) battery votage at ECM terminal ‘oxygen sensor heater relay (postion 73). See Fig, 1. 23 whenever the ignition is on. 4. Check for battery voltage at relay socket terminal 85 + It power is not present, check the wiring between, with the ignition key on. Check for battory voltage at relay terminal 87 in the fuseltelay panel and terminal lay socket terminal 30 (redvellow wire) in the relay pan» i 23 In the ECM connector (red/blue wire). If no wiring el with the engine running. i faults are found, the relay is most likely fui. + If voltage isnot present, check the wiring tothe rok” i ‘sookets. Voltage to terminal 85 is supplied via the ~ Hy ower supply relay and voltage to terminal 30 is, 1 To test oxygen sensor ‘supplied via the fuel pump relay i i heater relay (J208 or J278) i} dy 5. Reinstall he rela. Then working through the rear ofthe 4 Be sure both the main relay and the fuel pump relay aro relay, check for ground at relay terminal 31 (white wire functioning correcty before testing the oxygen senor heator with the engine running. relay. + Ht ground isnot present, check the wire between the relay and the Motronic ECM (terminal 28). Ifno wirin-—~ faults can be found, the ECM may be faulty. } + If no electrical faults are found up to this point, the relay is probably faulty and should be replaced... Table d. Motronic ECM Electrical Tests ; Gomponentor aout “Test terminals (atdiocon~ | Toe conditions Teatvalue rected ECM connoctor | J unless otherwiae noted) I ECM power supply (constant) | 7 (and 54 (4) = ‘i EOM power cuppy(owichod, 11 0) and 2a) duper tennials 8 and/68 af EON | Approx Baty volage 7, i from power supply ey) cancer | ooo supe relay wal coy 4 Ful pump relay (317) ‘Jumper terminals 6 and 55 | Tum ignition on Fuel pump rung, i Atel purprelay witeik) “> ‘ | Heated oxygen sensor relay” ayfindor engine only Jomperersnals 9 and 65 aiod angen eerstrelay h (6208 oF J278) | dumper terminas 1 and28 | Tuntigiton an closes/opens (clits) eas : bret tine wis connect Tears OA) | Janene | Tom moan 1 MIs up Vehici speed sensor VSS) | @eylinder engine ignion on 0-4 als (WACO), fuduating (G22) Tara's | Rese and opin ont ft wheel y | seyinaerengine ~~ Sas A enecoriverin-or | Seylinder engine Crs with manual transmission: shit "0-10 vos (VAG), fucuating | so andes lover n neural ) ‘ ~~ (eontinued on next page) ELECTRICAL CHECKS AND COMPONENT TESTING (1999-1995 racials)_ FUEL INJECTION-MOTRONIG 24a-13 Table d, Motronic ECM Electrical Tests (continued) ‘Component or art | Tet ierminals (at clscon- | Test condone sae nected ECM connector unless otherwise noted) Tain grounds GND) Tend = ~ Fee btn satage | “To ands ‘gine: NY and Gates 17 i 6-aynder engine: all models ~ [88 and 54 = _ Bands = ‘56 and 54 = ‘Approx batory vokage with AT only =~ ban volags Seand 54 Appr baer voage ‘with man.teana. only | — ‘Approx. Bary votage Teena sa “or “Feyiinder engine | Sdlocos lever in Park or Neuza i —| ae Tend 54 Igraon on AREY oRage ~ | €-cylinder engine | Selector lover in Park, “Approx. 2 vols less than tend? Disconneet connector rom ignition ool! | battery voltage ~ ‘and operate starter | AiG signal On signal 55 () and 20 (4) “Tum ignition on ‘Approx, batiery voltage | Tum fresh airciower on — | Tum A en "AIG compressor ‘Jumper iominals 37 and'38 | Ignifon on ‘NG compressor clutch rey cicks oach tme wires - comecied Fislinjoctor col enlanco ” ~ ~| ‘¢oylinder engine : F 10.1 (NSO) = 1421.5 ohms ro. 2(NSt) = 1421.5 ohms 10.8 (N32) = 1421 50hms ( ro. 4 (N39) = 1421.5 ohms ~ ‘Soylinder engine = 10.1 (N50) = 1421.5 ohm 10:2 (N81) 14215 ohms { 10.8 (N32) = 142150hms 10.4 (N33) = 1421.5 ohms 10.5 (NBS) — 1621.50hms Nes} = 14215 onms ae Evaporative (EVAP) canister = 40-60 ohms urge reguator vee (NEO) a ( [ Engine cociant temperature 4 and 33 l= Resistance varies with — | (EET) sensor (682) ‘temperature. See Engine | Coolant Temperature (ECT) Sensor (G62), (| Bata ink connect: (LOH 21 of EOMandieminal tet | ignite off "| Maximum 15 ohms 11999 and early 1994 white data lnk connector (See Fig, 6ahownearter) 10) - “43 of ECM andtorminal2 of | Igrition off _ ‘Maximum 4.5 ohms ito data irk cormector Le) _) | Data connector OL} 2 ofEOM andtorminel Sof | terion off Maximum 15 ohms Ilo 1668 and 105 16pin DLC (wire) Fia.8 ROPES em ear “®otEOMandiorminal tt | Tonion of 1 Maximam 75 ohms . 16pin DLC (Kwa) | ~ ~ (Continued on next page) ELECTRICAL CHECKS AND COMPONENT TESTING (1993-1995 models)24a-14 FUELINJECTION-MOTRONIC Table d. Motronic ECM Electrical Tests (continued) nected ECM connector «_| unless otherwise noted) ‘Component or crcult | Test forminals (at dlecon- | Tost conditions Test value Wiring ta healed oxygen sensor | 20 and 42 (G29) ‘Disoonnest oxygen sensorhamess | Maximum 7.5 ohms ‘connector (rear of encine) and jumper (G40) wing ‘Stile Sond ‘Reconnect connector: ~ Infinite ohms | “Trio postion (TP) censor | @Oandat = - Taji 181024 koe (eos) wing eBiner 18025 kote [— Taito coood Taji 1012.0 hms 3nd 40 eSpnder O70 19 Kons droite soviy | Reino nes Seosty . 40.and 41 ‘Throttle closed ~~ A-oyinder: 2.5 10.4.0 k ohms, eQincerasioesterne | ‘Open thrattle slowly ~~ | Resistance deorbasos y Beery ‘Camshaft position censor (CMP) ~~" Disgonnast harness conneotor from Maximum {5 ohms camshaft poston sensor and jumpor ferminale 1 (wbite/red wire) and 2 Mand ss i {rowniack obra) n “Ceyfinder engine 7 | ‘Dieconnet hamess carnector fem igniton al ouput sage Gis) wang AO aes Jumper terrinals 7 and in connector | Maximum 1.5 ofms “Band 38 ‘Jumper terminals 2 and 3 in connector | Maximum 7.5 ohms ‘Geylinderenging S| Diseonnect hamess connector from ignition coll. Recor ES Band 65 ‘Jumper terminals 1 and 2 in connector | Maximum 1.5 ohms: wanes “Tomperterinals 7 and comnester | Maximum 15 ofmis Vseends “Lump terminals 7 ard coredtor | Maximum 15 afm ‘38 and 65 Maximum 1.5 obms A Knock sensor | (G61) wing ~ | Bisconnect harness connector to knock sensor! (et rear of engine) ‘Baendae | Gompor terminals 7 and 2m conneaor | Maxam 15 ohms fn ohms ‘Jumper terminals t and th connector | Maximum ‘Knock sensor (G86) wiring 38and 56 ‘Bisoonnest hamese connector fo knock eeneor W (hear sari) ‘Jumper terminals 2 and 3h connector | Madman 1S ohms 87 and oS Tamportominaa Tanda connoaor | Wasimam 18 chs ‘sSand9s = Resistance varioa a ‘depending on temperature, ‘See To teat Intake alr temperaiure sensor Idle a contol (AG) valve (N71) | 27 and 59 = “Feyindor 710 10 ohms | S-oyiinder: 60 12.0hms (Continued on next pag ELECTRICAL CHECKS AND COMPONENT TESTING (1993-1995 models)FUEL INJECTION-MOTRONIC _24a-15 Table d. Motronic ECM Electrical Tests (continued) ‘Component or eicult | Test terminals (et discon- | Test conditions Test vaha nected ECM connector Unless otherwnae noted) : “Eoyfindor engine r Dinconnec hamiess connector rom MAF eanaar ‘Mass ait flow (MAF) senor (G70) — — ree wie Tange “lunportorninals and in connector | Waa iS ohms | Sanda “limber terminals + ard in comector | Mecrurt 12 oh tnd 1? “limpertominale tind 4in connector | Maxtnum 1c | eeylinder engine ~ Disconnect hamess connector from MAF sensor Mate a tow QAP eoneor(@70) weg vain pn canner ‘and 7 “lrnpa Tomine @ and in connector | Wana {ohms va Spin eonnedor Tand1@ | spar ermine and in eonnoator | Waainum {ohme Tend “umperteminals 1 and n connector Be ards “hevpertenrinals and 4 connector 1 and 23 | dumper terminal Vand 5 in connector Engine speediratoranos senaor | 67and68 -_ 500-700 ohms: (G28) Care wih EGA “wands isconnoat hamess connector fom | Manu Babe EGR tempore sensor (298) GR soorot ave (N10) and jumper termini | and in conrecor Gare wih EGR Band = Bai chm EGR vocuu rogultrslenod vave (N19) 20 and90 Disconnect hamess connector tom | Maximum 1 ohms ‘olonold valve ae jumper ernst | | andaincomectr ‘Scorday a injesion (AIR) dumper rminale @ and65 | Jamportenninale Tand 40 baal | AIA pump ely ela ach pump rely (1250) tie wie comeced ‘Secordar/ainjion AIR) | Janperiominals and 85 | Jonper terials and @biely | AI pump motor nme cash panp moor (viet) fie wke kommen ‘Secondary a isjecion (AIR) | arpa ieminals 9 and 85 | Jumpor terminals | and 50 braiy | AR ealnoid vako oleke soserad ve (113) Disconnect hamess| echt me comneted connector fro pup motor Engine Coolant Temperature (ECT) Sensor (G62) The ECT sensor is cite of the main inputs to the engine management system. its signal is used to adapt lantion tim- ing, injection time, and idle speed stabiization. In addition, the ECT signal is used to activate the knock control system, the idle speed control aystom, oxygen sonsor operation, fuel tank venting, and exhaust gas recirculation (EGR). ‘The ECT sensor sends continuous engine temperature in- formation to the Motronic ECM. I there isa break in the signal from the temperature sensor, the ECU will simulate a fixed ‘signal based on an engine temperature of 178 °F (80°C). (On 4-oylinder engines, the ECT sensor (G82) Is mounted in the coolant outlet an the rear of the cylinder head. The ECT sensor is combined with the temperature gauge sensor (@2) Ina single housing. The sensor body is black and the sensor has four terminals. Soe Fig. 11 Fig. 11, EGT sensoron 4-cyindor enghne, Chack sensor resltance at ‘erinals 1 (blue wie) and 3 (brownvereen te). ELECTRICAL CHECKS AND COMPONENT TESTING (1999-1995 models)24a-16 FUEL INJECTION-MOTRONIC On 6-cylinder engines, the ECT sensor Is mounted in the thermostat housing. The sensor body is blue and the sensor hhas two terminals. See Fig 12. Fig. 12. Ooolant sensor rangement on VR-6 engines, ECT sensce (662) (A-biie), coolant gauge senser (62) wih afterrun fan ‘suiteh (F87) (B-yalow), and AC thamal outat suitoh (F168) with thet speed cootent fan switch F165) {C-brown). Totost the ECT sensor, disconnect the hamess connector ‘and connect an ohmmeter across the sensor terminals with the engine cold, Start the engine and allow it to warm up. ‘Compare the meter readings to the graph shown in Fig. 13. If any faults are found, the seneor should be replaced. NoTe— On 4-eylnder engines, test aorass torminels 1 (tive wire) and 3 (orownforeon wire) In the sansor. Throttle Position (TP) Sensor (G69) ‘The TP sensor Is mounted to the side of the throttle vaise housing, directly connected to the throttle valve shaft. See Fig. 14. The ECM sends a §-volt reference signal into the" ‘sensor. Depending on throtle positon, the output voltage. ios in relation to the throttle position. Fig. 14, Thre postion sensor mounted to throttle valve housing. Test the TP sensor using the information given in Table d the test rosults are incorect, the sensor should be replaced” ‘The sensor is not adjustable, Use a new O-ring at trol housing when replacing the sensor. ° Check the reference voltage between terminals 1 and in ‘the 3-pin hamess connector. There should be approximate” § volts with the ignition on, Hf any faults aro found, check th.’ Wiring between the sensor and the ECM. If ne wiring faults can bbe found, the ECM may be faulty, 7 Q +——_|]—___»o sto 500 700 0 00 «00 300 200 ‘00 ae88888 0 10 2 40 40 60 60 70 80 $0 1000 Vas 075 3-18. Grech showing ooclant temporature sensor resistance vs. temperature, cauTION— ‘The signal trom the throttle position (TP) sensor ls ay ‘also used by the automatic tzansmiesion conto! ‘modtle (TCM). Vokswagen species that Ifthe ‘Motronle ECM, the TCM, the TP sensor or the {rote valve housing are replaced, the ECM and TOM ‘Basio Setings® should be “lated” using the special VA.G. 1551 scan tool. these basic settings are not done, transmission shitting and eveablty problems may be encountered. ELECTRICAL CHEGKS AND COMPONENT TESTING (1983-1995 models)Mass Air Flow (MAF) Sensor (G70) ‘The mass ar flow (MAF) sensor provides the engine load sig- nal to the ECM. The MAF sensor s located at the air iter hous- ing and electronically measures the air entering the engine. When the engine is running, an electrical current fs used to heat a thin wire oF fim in the sensor. The current flowing through the wire/lim is regulated to maintain a constant tam- perature above that ofthe intake airtemperature. The amount of current required to heat the wire isthe basis ofthe engine load signal. The MAF sensorhas no intemal moving parts and cannot be serviced, adjusted or accurately tested. See Fig. 15. Fig. 15. Hotfim mase air fow (MAF) sencor used on 4- end Ecyinder engines, Ifthere is no signal rom the mass air low (MAF) sonsor, the ECM automaticaly switches to a “Yimp-home” mode, turns on. the Check Engine ight, and stores a DTC tautt in permanent memory. The engine can stil be started and driven in the “limp-home” mode. To check mass air flow (MAF) sensor voltage and ground 1. Disconnect the harness connector from MAF sensor, 22. Tum the ignition key on and check for voltage between, terminals 1 (-) and terminal 3 (+) In the harness con- Rector. See Fig. 16 for terminal identification. + Hany faults are found, check the wiring to the MAF ‘sensor using the appropriate the diagram found in 97 Wiring Diagrams, Fuses, and Relays. FUEL INJECTION-MOTRONIC 24a-17 i waar Fig. 16. Mass ar fow (MAF) sensor hamees connector terminal ken ‘cation. Nore — ‘On 4-eyndor engines, check for of depasts on the sen ‘or element. Overtime ol vapors can colecton the sen. ‘507, owing to its mounted postion, Ifthe sensor # oi ‘contaminated and a MAF sensor DTC hes been stored, ‘the sensor is most tel futy and shoul be replaced. Fuel Injectors ‘The fuel injectors are elocticaly operated solenoid valves. ‘The Injectors are connected to a common fuel suppty, called tho fuel ral. See Fig. 17. Fuel pressure Fig. 17, Fuel ras common tue sup and mounting for ful Hctor, ELECTRICAL CHECKS AND COMPONENT TESTING (1983-1995 models)24a-18 FUEL INJECTION-MOTRONIC ‘The injectors are supplied 12 volts by the power supply re- lay and the ground side of the injectors are sequentially ‘switched on and off by the ECM. Injection quantity is basedon, the length of time the injectors are open. To test fuel injectors | ‘The information below’ an electrical test only. The test does: 1 ‘ot check injector spray pattems or fuel supply tothe injectors. i NoTE— 1 ‘tyau think an inectore bad, place a screwdriver or an ‘automotive stethoscope on the injector with the engine running. The injector should be buzzing. not, cheok | {or voltage to the injector and check its resistance as 1 , ‘ed/bive wire of each injector connector with the Ire. (on, See Fig. 19. tno, check the wiring tothe injactor. Fig. 18. Chock power to injactor connector with ignition en. Chee’ rectus wi of connactr arrow}, 4, If there is positive (x) battory voltage at the connec” but no pulsed ground signal, check the wiring botwe. the ECM and the injectors. no wiring faults can be found, the ECM may be faulty. - Oxygen Sensor (G39) ‘The heated oxygen sensor monitors the exhaust gas aie’ provides the Motronic ECM with feedback about the air-fus! Tatio and combustion etficiency. See Fig. 20. Using this in mation, the ECM continuously adjusts the air-luel mixture «x ‘ensure optimum criveabilty and exhaust emissions. The ser ‘Sor must be at a temperature of at least 600°F to gonor™’™> voltage, 80 itis electrically heated to help it reach operat...’ temperature more quickly. ‘The oxygen sensor producos a small voltage (0-1 w__) based on the oxygon content in the exhaust gas as comparéd to the oxygen outside the exhaust pipe, The bigger the citer: ential, the greater the output voltage, When the mixture is there is very litle oxygen in the exhaust (igh output votagey:” When the mixture is lean, there is an excess oF oxygen in exhaust (low output voltage | A ELECTRICAL CHECKS AND COMPONENT TESTING (1853-1995 mods)Fig. 20, Hosted oxygen sensor monitors exhaust gas. To test oxygen sensor +1. Working at the back side of the engine, locate the 4-pin ‘oxygen sensor hamess connector. WARNING— Use care when working near a hot engine. The ex hhaust pipes and the engine surfaces can cause se- vere burns. 2. Without disconnecting the harness connector, connect the positive iead of a voltmeter to terminal 4 (signal wire) of the connector. See Fig. 21. Connect the nega- tive lead to chassis ground. Fig. 21. Cxygen sensor harness connector trina denticaton. 3. Stat the car andlet tile. The oxygen sensor should stat to produce a fluctuating votage within a short period. ‘Oxygen sensor output signal + voltage at ide 0.3 to 4.0 volt fluctuating FUEL INJECTION-MOTRONIC _24a-19 NoTE— To futher check sensor response to lean and rich mix tures, briefy dlsconnect an injector connector or pach Off the vacuum hose fuel pressure regulator and ob serve the sensor response. 4, Htthe sensor output is incorrect, turn the engine off and Chock the sensor heater crc Disconnect the four ire connector and check for battery voltage at termi- rials 1 and 2 with the engine running. + Ht voltage is not present, check the wiring to the heater. + Htvoltage is present, check the heater coll resistance: ‘across terminals 1 and 2 of the sensor side of the Connector, If any faults are found, replace the sensor. ‘Oxygen sensor + heater resistance... approx. 2 ohms: 6. Ifthe axygan sensor signal Is not as specified; and the heater clout is OK, the sensor may be faulty, Nore— {fhe sensor signa is eer very ow or very high and fuctasing slighty, the Moronc adapabiy ls may have been reached. Look for signs of rh low output ‘gna or lean (igh output signal running charactrs- tas botore replacing to oxygen senso. Tightening Torque + Oxygen sensor to exhaust pipe . .... 50 Nm (97 ftlb) NoTE— Coat the oxygen sensor threads with an anti-selze ‘compound before instalation, Bo nat get the com pound on the sensor tp, This can damage the sensor. Idle Air Control (IAC) System The Motronio ECM electronically controls the idle speed ‘through the IAC valve (N71). See Fig. 22. The system auto- ‘matically compensates for engine load and engine operating ‘conditions, so periodic adjustment of the idle speed is unnec- essary The Motronic ECM monitors engine rpm and other operat- ing conditions such as alt conditioning and automatic trans~ ‘mission loads, and then sends an electrical signal to open or Close the valve. This changes the amount of airthat bypasses the closed throttle valve, ELECTRICAL CHECKS AND COMPONENT TESTING (1993-1995 models)‘CAUTION (Do not atop to correct a faulty the idle speed by adjusting the postion of the throttle valve stop ‘sorew. the factory setting ofthis screw i aterod, the complete throttle housing wil need to be re- laced—no adjustment specifications are aval. able fom Volkswagen. See Component eplacoment. ‘The IAC function is completely adaptive, The ECM remem- bers how far the valve was open the last time the engine was at idle and reverts to this as a base seting, in addition, the ‘lve has a limp-home feature that maintains a fixed idle speed in the event of an IAG valve failure. NoTe— (On high miteage cars, enough residue may collect on the throttle valve plate and bore to restrict alr fow and afc! the JAC system. It heavy rosidue fs found, clean ‘bath the IAC valve and tho throtle pate and bore be- fore clagnosing IAC problems. Before proceeding with troubleshooting an idle problem, ‘check that the throttle position sensor is working correctly as described earlier under Throttle Position Sensor. To test IAC system . 1. With the engine running, grasp the IAC valve and check that itis buzzing, . not, stop the engine and disconnect the hamess con- hector from the valve. Check the resistance of the valve. ‘aoross its terminals. If resistance Is Incorrect, replace the valve NoTE— ‘you suspect an intermitent faut ight tap the valve While You are testing resistance. 1AC Vatve current, engine idling .......-... + duty cycle, engine idling NoTE— + Ifthe idle speod is high and the curent draw is also ‘high or ifthe idle speed is tow andthe low, the probiom is mosttkely 2 fauty electrical Inout 1 the ECM, toling to maintain an inoonectiofo spoed. (Le. engina speed signal, three position, ourentdraw ie 24a-20 FUEL INJECTION-MOTRONIC _ - Teobece IAC Valve man runture + resistance. . oo 60 12 chins Aematire rs “ae ween ee 8. Connect an ammeter to the valve and check the va... cent craw withthe engine fling, favallabl, conse a diy cycle meter fo the valve according tothe men, facturer’s instructions. Check that the current anc. duty cycle are within the specified ranges. Be. + If there is no signal at the valve, cheok the wiring - ‘ate between the ECM and the valve. See 97 Wiring __) boot Diagrams, Fuses and Relays. 620+ 20 mA AVC-on signals, and A/T dive postion) - + Ut the tole speed is low or normal bu the curent craw ~ Js high orf the idle spoed is high oF nermel, but the ‘current craw is low, the problem is mast likely a me- ‘henical problem, such as stuckauty IAC valve or 2 ‘malachusted throttle plate, Camshaft Position (CMP) Sehsor (G40) ‘The camshattposition (Hall) sensor identities oyinder pe” tion for sequential fue injection and knock regulation. Orr oyfinder enginas, the camshaft position sensor fs mounted within the ignition distributor. On 6-cylindor engines, the sr ‘ors mounted in the end ofthe cylinder head, n the cart. sprocket cover. To test CMP sensor 1. Romove fuse 16 from the main fuse/rotay panel, 2, Disconnect the harness connector from the camshaft position sensor. a 8. Connect a voltmeter betwoen the two outer terminals in the connecior and check for voltage with the ignito= key on. Ht voltage is not present, check for wiring fau, using the appropriate wiring diagram, *On 4-cylinder engines, there should be a minimum o* svt, On 6-oVlinder engines, there shouldbe & minimum of To-vols. ELECTRICAL CHECKS AND COMPONENT TESTING (1998-1985 models)4 If voltage is present, peel back the protective rubber boot.on the Hall sensor harness connector and then re- ‘connect Ito the sensor. Connect an LED test light be- ‘tween the center terminal and ether of the outer torminats. 5. Wiién the starter Is actuated, the LED should flcker. it there is no reaction, the Hall sensor Is defective and, ‘should be replaced. See Component Replacement. Nore — (On 4-cyiinder engines, the Hal sonsor I not separately available from Volkswagen. If the sensor s faulty, the ‘complete cstibutor body wil need tobe replaced. Engine Speed (RPM) Sensor (G28) The engine speed (rpm) sensor supplies engine speed and crankshaft (cylinder no. 1 TDC) position signals to the Motron- ic ECM. The sensoris mounted on the intake side of the cyiin- dor Block and reads a toothed wheel mounted on the end of the crankshaft. Soe Fig. 23. It this sensor is faulty, the engine will not star. To check for a faully sensor, crank the engine for at least six seconds and then check for a stored fault code (DTC) in the On-board Diag nostic memory as described earlet under Diagnostic Trot ble Codes. Crankease Tas Fig. 23, Enghe speed (FI sensor (828) euppitos engine apded and ‘rankchatt postion. TDG is signaled by twortcath gap in whoo FUEL INJECTION-MOTRONIC 24a-21 Carefully inspect the toothed wheel on the crankshaft for damage or deformed teeth. This can be accomplished through the sensor mounting hole or by removing the cil pan. There should be 68 teeth plus a 2-ooth gap on the wheel for ‘both 4-cylinder and V-6 engines. The toothed wheel can be replaced, but requires removal ofthe crankshaft Engine Speed (RPM) Sensor + coil resistance, «+ 800-700 ohms Intake Air Temperature (IAT) Sensor (G72) ‘The intake air temperature (IAT) sensor sends continuous intake air temperature information to the Motronic ECM. This Input is used primarily as a correction factor for lantion timing. HH there is a break in the signal from the IAT sensor, the ECU will simulate a fixed signal based on an engine temperature of approximately 68°F (20°C). ‘Totest the IAT sensor, disconnect the hamess connector and ‘connect an ohmmeter across the sensor terminals, Soe Fig. 24, ‘Compare the meter reading to the graph shown earfer in Fig. 18. Itany fautts are found, the sensor should be replaced. oe Fig. 24 intake a temperature enor (arrows) in Intake rails {6-ofinder engine shown) ELECTRICAL CHECKS AND COMPONENT TESTING (1993-1895 models)I t fl te 24a-22 FUEL INJECTION-MOTRONIC COMPONENT REPLACEMENT (1993-1995 models) To remove and install Motronic Engine Control Module (ECM) ‘The ECM is mounted inthe rear of the engine compartment, Inthe right-hand side of the air plenum. See Fig. 25. Fig. 25. Motronic EOM In a plonum at reer of engine compariment, 1. Wait at least one minute, then disconnect the negative (© battery cable. 2. Unplug the harness connector from the ECM by releas- ing the fastener end then pivoting the connector off the madul. 98. Remove the mounting bracket nut and remove the ECM togethor with its brackot. 4, Installation is the reverse of removal. To remove Engine Coolant ‘Temperature (ECT) sensor For ECT sensor location on 6-cylinder, see Fig. 18 glven ear. 1. Drain approximately one gallon of coolant from the cook {ng system. This is to prevent coolant from leeking out when the sensor is temoved. See 19 Engine-Cooling ‘System, COMPONENT REPLACEMENT (1998-1995 models) 2, Disconnect the senor harness connector. 3, Remove the sensor retaining clip and pull the sens.. ‘rom its housing. See Fig. 26 Fig. 26, ECT sensor retaining cp arrow) on 4-cylnder engine, ~ Instalation is the reverse of removal. Clean the sensor sealing surfaces and use a new O-ring whan reinstalling th~ sensor. To remove Throttle Position (TP) sensor. ‘Volkswagen species that if the TP sensor is replaced, the. engine control module (ECM) and transmission contro! mo\ tle (TCM) “Basic Settings” should be “intiated” using the sps* lal V.AG. 1851 scan tool. The throto position signals used. by the ECM and the TCM. ifthese basic settings are not dor using the scan tool, transmission shiting ‘and drivoabilty- problems may be encountered. 1. Unplug the hiamess connector from the sensor. See Fi. 14 glven earlier. 2. Remove the mounting scraws holding the sensor to th side of the throttle vaive housing. Remove tha sensor and its O-ring. Installation is the reverse of removal. Use a neW O-ring andr tighten the screws to the specified torque. Tightening torque “TP sensor to throttle valve housing ....8 Nr (27 jnb)~__ FUEL INJECTION-MoTRONIC _24a-23 To remove Mass Air Flow (MAF) sensor 1. Loosen the large hose clamp securing the rubber duct ‘to the mass air flow (MAF) sensor. Remove the duct from the sensor. 2, Disconnect the harness connector from the MAF sensor. 3. On 4oylinder engines, remove the two mounting ‘screws holding the MAF sensor to the upper air cleaner housing. 4, On G-cylinder engines, loosen the clamping band hold- Ing the MAF sensor to the upper alr cleaner housing. See Fig. 27. Tightening torque + MAF sensor to air cleaner housing (4-cylinder) ++ 10.Nm (89 inb) To remove fuel injectors Cleantinessis important when working with uel ceuitcom- ponents. Thoroughly olean the unions before dicconneeting any fuel lines, Use clean tools. WARNING — Fuel wil be expeied when tual nes are disconnect- ‘ed, Do not smoke or work near heaters oF other fre hazards. Keop a tre extinguisher handy. 11. Remove the upper intake manifold and related compo- rents. Cover the open intake runners using clean shop rags. See 18a or 15b Cylinder Head and Valvetrain. 2. Unplug the wiring harness connectors from the injéctors. Disconnect the fuel supply and retum hoses from the fuel rall, See Fig. 28. RF sana? 1. filer oust ‘Upper na 6. Intake air duct 2. irleaner olement 7, Fiting frie taitzer & figpener nowy Ta eppcabl for 08D 1 4. Oring 1 2 3 4 ‘aa Fig. 27. Mass airflow (MAF) sensor on S-cyinder engine, '5. Remove the mass airflow (MAF) sensor from the ait Gleaner housing Installation isthe reverse of removal. Replace the O-ring Itt ia damaged. WARNING — Wrap a claashap towel around the fual ine ftings ¥ betore loosening them. NoTE— The fue! supply line ls marked with white and the retur Ino is marked with blue, 4, Remove the bolts that hold the fuel rail to the intake ‘manifold and pull the fuel rll away complete with injec- ore 5. To remove the injectors trom te tel ral, pry ofthe re- taining cps, then twist the injectors slightly and pull them off When installing the injectors, lightly lubricate the O-rings with engine oi, Install the injectors tothe fuel rall but do not in- Stall the retaining clips. Position the fuel ral and injectors on the intake manifold. Make sure that injectors and the fuel rail are fully Seated and then instal the retaining clips and mount- ing bolts. Reconnect the fuel hoses to the fuel rail Install the upper intake manifold using a new gasket. Tightening torques + Upper intake manifold to lower intake manifold 4+oylnder engine. + 20.Nm (15 ftp) E-eylinder engine. » 25 Nm (18 ftp) (COMPONENT REPLACEMENT (1993-1905 modes)24a-24 FUEL INJECTION-MOTRONIC 4. Intake mantiold, upper 2. Wiring bamess: 3, Test comeetion plug i 4. Fuel supply lino 5. Fuel return ine 6 Ful rll Bolt ‘tighten to 10 Nen (88 nse) 8 Bolt ‘Tight fo 25 Nm (18 fb} 8. Intake manitold, lower i 10, Gasket i ‘always replace 11. Ong replace 12. Fuel injector 18 Retaining oip i 14. Fuel pressure regulator 15. Injector harness connector uw 16. Intake alr temperature (IAT) sensor | ettontoso ne | 1, var ne hen a Fig. 28. Fue rll assembly on 6-cyinder engina, To remove fuel pressure regulator WaRwinig— Fuel undo pressure wi bo expoted whon te fui prossre regulator is removed. Do not smoke ot Work near heat roar re hazats Kap a te lntnguisher hand 1. Disconnect the vacuum hose from the regulator. See Fig. 29. \ 2, Remove the fuel pressure regulator retaining clip. Wrap a shop towel around the regulator and then pull trom f the fue ral ‘ Installation isthe reverse of removal. Inspect tho Orings and replace ther if damaged. To remove Idle Air Control (IAC) valve 1. Disconnect the hamess connector from the IAC valve. Fig. 29. Fuel pressure regulator retaining clip arrow, 2, Loosen the vaNe's hose clamps and disconnect the hoses from the valve. 4, Remove the valve from its bracket, ‘3. On 4-cylinder engines, loosen the clamping bolt on the Installation s reverse of removal. valve's bracket. See Fig. 30. (COMPONENT REPLACEMENT (1993-1996 models)Fig. 20. IAC vave clamping bracket on 4-cyner engine arrow) To remove throttle valve housing Volkswagen specifies that If the throttle valve housing is re- placed, the engine control module (ECM) and transmission ‘control module (TOM) “Basic Settings” should be “initiated” using the special V.A.G, 1551 scan tool these basic settings are not done using the scan tool, transmission shifting and driveability problems may be encountered. 1. Remove intake air duct from the throttle valve housing. 2, Disconnect the throttle position sensor hamess con- nector and the accelerator cable from the throttle valve housing. 8. On 4-oylinder engines, disconnect the evaporative ‘emissions vent hose from the throttle valve housing. 4, On 6-oylindor ongines, relieve the cocling system pres- sure by removing the cap from the coolant expansion ‘tank. Clamp off the coolant hoses at the throttle valve housing and remove the hoses. 5. Remove the bolts holding the throttle valve housing to the intake manifold and remove the housing. Inctallaton isthe roverse of removal. Use @ new gasket dur- Ing inctallation. Hf roplacing the throtle valve housing, transfer all parts from the old housing tothe new one. On cars with manual {ransmission, ads the throtte dashpot as descrlbed below. FUEL INJECTION-MOTRONIC _24a-25 Tightening torques: + Throtie position sensor to throttle valve housing . . -3.Nm (27 in) + Throttle valve housing to intake manifold 4-cylinder engine. . sees 25m (18 fb) 6-oylinder engine : 10. Nm (89 intb) <= BO1Nm (14 ftb) To adjust throttle dashpot {cars with manual transmission) The dashpot is mounted to the throttle valve housing and holds the throttle valve open for a moment when the throttle is ‘suddenly closed. This helps reduce exhaust emission of un- burned fuel. NoTE— Botore making the adjustment below, check thatthe ttrotie valve stop screw poston has not been altered. the factory setng ofthis screw has boen tampered with, tho tote valve housing wil need to bo re- placed—no adjustment speciications are avaiable ‘rom Volkswagen. 1. Inserta 8 mm dril bit or fosler gauge between the throt- tle valve stop screw and the throtle lever. Soe Fig. 31 rd Fig. 31. Dil bt (3 mm) inerted between hottle vake stop screw and, throttle lver on 4-oynder engine. 2, Loosen the dashpot lock nut. Turn the dashpot unt its rod Just makes contact with the lever roller, Tighten the Jocknut. Remove the dri bit. Dashpot Adjustment Specifications i «+ 25-85 mm (0.98-0.138) 23.0 mm (0.118 in) COMPONENT REPLACEMENT (1993-1985 models)