EG2–183

ENGINE – MFI SYSTEM

TROUBLESHOOTING WITH VOLT OHMMETER

HINT: Because the following troubleshooting procedures are designed for inspection of each
separate system, the actual troubleshooting procedure may vary somewhat.
However, please refer to these procedures and perform actual troubleshooting, conforming to the
inspection methods described.
For example, it is better to first make a simple check of the fuses, fusible links and connecting
condition of the connectors before making your inspection according to the procedures listed.
The following troubleshooting procedures are based on the supposition that the trouble lies in
either a short or open circuit in a component outside the –computer or a short circuit within the
computer. If engine trouble occurs even though proper operating voltage is detected in the
computer connector, then the engine control module is faulty and should be replaced.
FUSES AND FUSIBLE LINK LOCATION
EG2–184
ENGINE – MFI SYSTEM

MFI SYSTEM CHECK PROCEDURE

HINT:
• Perform all voltage measurements with the con–
nectors connected.
• Verify that the battery voltage is 11 V or more
when the ignition switch is in ”ON” position.
Using a voltmeter with high impedance (110 k
/V
minimum), measure the voltage at each terminal of
the wiring connectors.

Engine Control Module (ECM) Terminals

Symbol Terminal Name Symbol Terminal Name Symbol Terminal Name
DISTRIBUTOR VOLUME AIR FLOW METER BATTERY B+
DISTRIBUTOR SENSOR GROUND EFI MAIN RELAY
DISTRIBUTOR VOLUME AIR FLOW METER
DISTRIBUTOR HEATED OXYGEN SENSOR EFI MAIN RELAY
IGNITER INTAKE AIR TEMP. SENSOR
VEHICLE SPEED SENSOR THROTTLE POSITION SENSOR
TCM SOLENOID ENGINE COOLANT TEMP. SENSOR A/T OIL TEMP. WARNING LIGHT
PARK/NEUTRAL POSITION SWITCH THROTTLE POSITION SENSOR SENSOR GROUND
TCM SOLENOID KNOCK SENSOR MALFUNCTION INDICATOR LAMP
PARK/NEUTRAL POSITION SWITCH EGR GAS TEMP. SENSOR O/D MAIN SWITCH
TCM SOLENOID HEATED OXYGEN SENSOR STOP LIGHT SWITCH
PARK/NEUTRAL POSITION SWITCH T/F FLUID TEMP. SENSOR
TCM SOLENOID 4WD OIL TEMP. SENSOR PATTERN SELECT SWITCH
TRANSFER POSITION SWITCH D LC1
VSV (for EG R) D LC 1 4WD SWITCH
IGNtTER DLC1 A/C AMPLIFIER
COLD START INJECTOR VEHICLE SPEED SENSOR
VSV (for EG R) DLC1
HEATED OXYGEN SENSOR A/C MAGNET SWITCH
VSV (for PAIR) CRUISE CONTROL ECU
ENGINE GROUND STARTER SWITCH
VSV (for A/C)
INJECTOR
INJECTOR
ENGINE GROUND
ENGINE GROUND

*1: A/T only *2: 4WD A/T only *3: California only *3: California and C & C *4: 4WD only *5: California 2WD only
Engine Control Module (ECM) Terminals
 EG2–185
ENGINE – MFI SYSTEM

Engine Control Module (ECM) Wiring Connectors Voltage

No. Terminals Condition STD voltage See page

EG2–186
Ignition SW ON

Throttle valve open

Ignition SW ON Throttle valve fully closed EG2–188

(Throttle opener must be cancelled first)

Throttle valve fully open

Ignition SW ON Measuring plate fully closed

Measuring plate fully open

Idling EG2–190
3,000 rpm
Ignition SW ON Intake air temperature 20
C (68
F)

Ignition SW O N Engine coolant temperature 80
C (176
F) EG2–192

Cranking EG2–193

Ignition SW ON EG2–194

Idling EG2–195
No trouble (malfunction indicator lamp off) and engine running EG2–196

Cranking Engine coolant temperature 80
C (176
F) EG2–197

Stop light switch ON EG2–198

Engine Control Module (ECM) Terminals

V02242
EG2–186
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

No voltage
Ignition switch 4N

• BATT– El

(1) There is no voltage between ECM terminals BATT and E1.

(2) Check that there is voltage between ECM terminal BATT and
body ground.

(3) Check wiring between ECM terminal E1 and

body ground.

BAD

Try another ECM. Repair or replace.

BAD
Check fuse and fusible link. Replace.

Check wiring between fuse and BAD

ECM. Repair or replace.
 EG2–187
ENGINE – MFI SYSTEM

• +B (+B1) –E1
(1) There is no voltage between ECM terminals + B (+ B1) and E1.
(IG SW ON) .

(2) Check that there is voltage between ECM terminal + B (+ B1 ) and

body ground. (IG SW ON)

(3) Check wiring between ECM terminal El and

body ground.

SAD

Try another ECM. Repair or replace.

Check fuse, fusible link and ignition BAD

switch. Repair or replace.

BAD
Check EF 1 main relay. Replace.

Check wiring between E F I main relay BAD Repair or replace.

and battery.

Check wiring between EFI main relay BAD

Repair or replace.
and ECM terminal + B (+B1).
EG2–188
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

Throttle valve open

Ignition Throttle valve fully closed

No voltage switch O N (Throttle opener must be
cancelled first)
Throttle valve fully open

• IDL – E2 (E21)

(1) There is no voltage between ECM terminals IDl. and E2 (E21).

(IG SW ON) (Throttle valve open)

(2) Check that there is voltage between ECM terminal + 131 (+ B ) and
body ground. (IG SW ON)

BAD
Refer to No. 1. Replace or repair.

Check wiring between ECM terminal E1 and body

ground.

BAD

Replace or repair.

BAD

(3) Check throttle position sensor.

BAD

Replace or repair throttle Check wiring between ECM and

position sensor. throttle position sensor.

Try another ECM.

 EG2–189
ENGINE – MFI SYSTEM

• VC – E2 (E21)

(1) There is no voltage between ECM terminals VC and E2 (E21).

(IG SW ON)

Check that there is voltage between ECM terminals + B1( + B) and E1.
(IG SW ON)

(2) Check throttle position sensor. Refer to No. 1.

BAD

Repair or replace. Check wiring between ECM and

throttle position

BAD

Repair or replace
Try another ECM.
wiring.

• VTA – E2 (E21)

(1) There is no voltage between ECM terminals VTA and E2 (E21).

(IG SW ON)

(2) Check that there is voltage between ECM terminals VC and E2 (E21) .
(IG SW ON)

Perform inspection of
VC – E2 (E21).

(3) Check throttle position sensor. BAD Repair or replace.

Check wiring between ECM and BAD

throttle position sensor. Repair or replace.

Try another ECM.

EG2–190
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

Ignition
SW ON Measuring plate fully dosed
No voltage Measuring plate fully open
Idling
IG SW ON Intake air temperature 20°C (68°F

• VC – E2 (E21)

(1) There is no voltage between ECM terminals VC and E2 (E21).

(I G SW ON)

(2) Check that there is voltage between ECM terminal + B (+ 131) and
body ground. (IG SW ON)

(3) Check volume air flow meter. Refer to No. 1.

BAD

Replace or repair volume Check wiring between ECM and volume

air flow meter. air flow meter.

BAD

Try another ECM. Replace or repair wiring.

 EG2–191
ENGINE – MFI SYSTEM

• VS – E2 (E21)

(1) There is no voltage between ECM terminals VS and E2 (E21).

(IG SW ON)

(2) Check that there is voltage between ECM terminals VC and E2 (E21).
(IG SW ON)

Refer to VC – E2 (E21). BAD Repair or replace.

b Check volume air flow meter. BAD

Repair or replace.

Check wiring between ECM BAD

Repair or replace.
and volume air flow meter.

Try another ECM.

• THA – E2 (E21)
(1) There is no voltage between ECM terminals THA and E2 (E21).
(IG SW ON)

Check that there is voltage between ECM terminal + B (+ B1) and

body ground. (IG SW ON)

(2) Check intake air temp.

sensor. Refer to No. 1.

BAD

Replace volume air flow Check wiring between ECM and

meter. volume air flow meter.

BAD

Repair or replace
Try another ECM.
wiring.
EG2–192
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

Ignition switch Engine coolant temperature

No voltage 80
C (176
F)
ON

(1) There is no voltage between ECM terminals THW and E2 (E21).

(IG SW ON)

(2) Check that there is voltage between ECM terminal +B (+ B1)

and body ground. (IG SW ON)

Refer to No. 1.

Check wiring between ECM terminal E1 and body ground.

BAD

(3) Check engine coolant temp. sensor. Repair or replace.

BAD

Replace engine Check wiring between ECM and engine

coolant temp. sensor. coolant temp. sensor.

BAD

Try another ECM. Repair or replace.

 EG2–193
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

No voltage Cranking

(1) There is no voltage between ECM terminals STA and E1.

(IG SW START)

Check starter Check wiring between . ECM terminal STA

operation. and starter terminal 50.

BAD BAD

Repair or replace.

(2) Check wiring between ECM terminal E1 and body

ground..

BAD

Repair or replace.

Check fusible link, battery, wiring BAD

and ignition switch. Repair or replace.

(3) Check that there is voltage at terminal 50 of starter.

(IG SW START) STD voltage: 6 V or more

Check wiring between ignition switch ST1

Check starter. terminal and starter terminal 50.
EG2–194
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

No voltage Ignition switch ON

(1) There is no voltage between ECM terminals # 10 and/or # 20

and E01 and/or E02. (IG SW ON)

(2) Check that there is voltage between ECM terminal # 10 and/or

# 20 and body ground,

Check wiring between ECM terminal E01 and/or

E02 and body ground.

BAD

Try another ECM. Repair or replace.

Check fusible link and ignition

BAD Repair or replace.
switch.

Check resistance of magnetic coil in each injector.

STD resistance: 13.4 – 14.2 Ω

Replace injector.

Check wiring between ECM

terminal # 10 and/or # 20 BAD Repair or replace.
and battery.
 EG2–195
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

!GT – E1 No voltage Idling Pulse generation

(1) There is no voltage between ECM terminals IGT and El.

(idling)

(2) Check that there is voltage between ECM terminal IGT and
body ground. (idling)

(3) Check wiring between ECM terminal E1

and body ground.

BAD
BAD
Refer to No. 1. Repair or replace.

Check wiring between igniter BAD

and distributor. Repair or replace.

Check distributor. BAD

Replace.

Check wiring between ECM and BAD

Repair or replace.
igniter.

BAD
Check igniter. Repair or replace.

Try another ECM.

EG2–196
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

No trouble (malfunction indicator

No voltage
lamp off) and engine running

(1) There is no voltage between ECM terminals W and El.

(idling)

(2) Check that there is voltage between ECM terminal W and body
ground.

(3) Check wiring between ECM terminal E1 and body

ground.

BAD
Try another ECM. Repair or replace.

Check GAUGE fuse

(10A) and malfunction indicator lamp.

BAD

Repair or replace.

Fuse blows again

Check wiring between ECM BAD

Repair or replace.
terminal W and fuse.
 EG2–197
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

Engine coolant temperature

No voltage Cranking 80° (176° F)

(1) There is no voltage between ECM terminals STJ and E1.

(IG SW START)

(2) Check that there is voltage between ECM terminal + B (+ B1 ) and

body ground. (IG SW ON)

(3) Check cold start injector. Refer to No. 1.

BAD

Replace cold start Check wiring between ECM and

injector. cold start injector.

BAD

Check wiring between ECM terminal E1 and body ground.

Repair or replace
Try another ECM. wiring.
EG2–198
ENGINE – MFI SYSTEM

No. Terminals Trouble Condition STD Voltage

No voltage Stop light switch ON

(1) There is no voltage between ECM terminals STP and E1.

(2) Check that there is voltage between ECM terminal STP and
body ground when the brake pedal is depressed.

(3) Check wiring between ECM terminal E1 and body

ground,

BAD

Try another ECM. Repair or replace.

Check STOP fuse 15A) and stop BAD

light switch. Repair or replace.

Check wiring between ECM terminal BAD

Repair or replace.
STP and battery.
 EG2–199
ENGINE – MFI SYSTEM
EG2–200
ENGINE – MFI SYSTEM

(1) There is no voltage between ECM terminals 11F and E1.

Check that there is voltage between ECM terminal VF and body ground.

Check wiring between ECM terminal E1 and body ground.

BAD
Try another ECM. Repair or replace.

YES
Is air leaking into air induction system? Repair air leak.

BAD
Check spark plugs. Repair or replace.

BAD
Check distributor and ignition system. Repair or replace.

Check fuel pressure. BAD Repair or replace.

Check injector. BAD Repair or replace.

Check cold start injector.* BAD Repair or replace.

Check volume air flow meter. BAD Repair or replace.

Check operation of heated oxygen

sensor. System normal.

BAD
Check wiring between heated oxygen BAD
sensor and ECM connector. Repair wiring.

Replace heated oxygen sensor. *Rich malfunction only

 EG2–201
ENGINE – MFI SYSTEM

(1) There is no voltage between ECM terminals THG and E2 (E21).

(Engine running at 2,000 rpm)

(2) Check that there is voltage between ECM terminal + B (+ B1) and
body ground. (IG SW ON)

Refer to No. 1.

Check wiring between ECM terminal E1 and body ground.

BAD
Repair or replace.

Check EGR system. BAD Repair or replace.

Check EGR gas temp. sensor.

BAD

Replace EGR gas temp. Check wiring between ECM and

sensor. EG R gas temp. sensor.

BAD

Try another ECM. Repair or replace.