Motronic self-diagnosis

Display group overview

Display group
Indicated on display Designation
no.

Read measured value

00 1 = Coolant temperature
block 0

1 2 3 4 5 6 7 8 9 10 2 = Engine load

3 = Engine speed

4 = Battery voltage

5 = Throttle valve angle

6 = Control value, idling air mass

7 = Learned value, idling air mass

8 = Control value for mixture formation (lambda control

value)

9 = Learned value for mixture formation (lambda learned

value), additive

10 = Learned value for mixture formation (lambda learned

value), multiplicative

Read measured value

01 1 = Engine speed
block 1

Basic 1234 2 = Engine load

function 3 = Throttle valve angle

4 = Ignition angle

Read measured value

02 1 = Engine speed
block 2

Basic 1234 2 = Engine load

function 3 = Injection period

4 = Air mass

Display group no. Indicated on display Designation

03 Read measured value 1 = Engine speed

Basic function block 3 2 = Battery voltage
 3 = Coolant temperature
1234
4 = Intake air temperature

1 = Throttle valve angle

2 = Idling air mass, learned (no gear engaged on
automatic)
3 = Idling air mass, learned, with gear engaged on
04 Read measured value
automatic
Idling speed block 4
4 = Operating status: Idling
adjustment 1234
Part throttle
Full throttle
Overrun
Enrichment

1 = Engine speed (actual)

05 Read measured value
2 = engine speed (specified)
Idling block 5
3 = Idling speed control
stabilisation 1234
4 = Air mass

1 = Engine speed
06 Read measured value
2 = Idling speed control
Idling block 6
3 = Lambda control
stabilisation 1234
4 = Ignition angle

Display group no. Indicated on display Designation

1 = Lambda control
2 = Lambda probe voltage
07 Read measured value
3 = Duty cycle, solenoid valve 1 for activated
Lambda control and ACF block 7
charcoal filter -N80
system 1234
4 = Lambda correction factor with active tank
breather

1 = Injection period
2 = Lambda learned value at idling (additive)
3 = Lambda learned value at part throttle
08 Read measured value
(multiplicative)
Lambda block 8
4 = Tank breather system: TB active (tank
learned values 1234
breather active)
Lambda adaptation (tank breather
not active)

1 = Engine speed
09 Read measured value
2 = Lambda control
Lambda block 9
3 = Lambda probe voltage
learned values 1234
4 = Lambda learned values at idling (additive)

1 = Duty cycle, solenoid valve 1 for activated

charcoal filter -N80
10 Read measured value
2 = Lambda correction factor with active tank
Tank block 10
breather
breather 1234
3 = Fill factor of activated charcoal filter -N80
4 = ACF purging quantity

11 Read measured value 1 = Engine speed

Fuel block 11 2 = Engine load
 3 = Vehicle speed
consumption 1234
4 = Fuel consumption

Display group no. Indicated on display Designation

12 1 = Engine speed
Read measured value
Fuel 2 = Battery voltage
block 12
consumption during 3 = Fuel consumption
1234
idling 4 = Ignition angle

1 = Ignition timing retardation by knock control,

cylinder 1
2 = Ignition timing retardation by knock control,
13 Read measured value
cylinder 2
Knock- block 13
3 = Ignition timing retardation by knock control,
control 1234
cylinder 3
4 = Ignition timing retardation by knock control,
cylinder 4

1 = Engine speed
2 = Engine load
14 Read measured value
3 = Ignition timing retardation by knock control,
Knock- block 14
cylinder 1
control 1234
4 = Ignition timing retardation by knock control,
cylinder 2

1 = Engine speed
2 = Engine load
15 Read measured value
3 = Ignition timing retardation by knock control,
Knock- block 15
cylinder 3
control 1234
4 = Ignition timing retardation by knock control,
cylinder 4

1 = Knock sensor signal, cylinder 1

16 Read measured value
2 = Knock sensor signal, cylinder 2
Knock- block 16
3 = Knock sensor signal, cylinder 3
control 1234
4 = Knock sensor signal, cylinder 4

Display group no. Indicated on display Designation

1 = Engine speed
17 2 = Engine load
Catalytic converter- Read measured value 3 = Energy balance for cat warm-up (ADR
warm-up and/or distributor block 17 engine)
basic 1234 Position of Hall sender signal (ADP
setting engine)
4 = Ignition angle

1 = Engine speed
2 = Engine load without altitude
18 Read measured value
compensation
Altitude block 18
3 = Engine load after altitude
compensation 1234
compensation
4 = Altitude correction factor
 1 = Engine speed
19 Read measured value
2 = Engine load
Torque block 19
3 = Retardation of ignition angle
reduction 1234
4 = Ignition angle

1 = Engine speed
20 Read measured value
2 = Selector lever position
Operating block 20
3 = Air conditioner/rear window
states 1234
4 = A/C compressor

21
1 = Engine speed
Operating Read measured value
2 = Engine load
states block 21
3 = Coolant temperature
Lambda 1234
4 = Lambda control ON/OFF
control

Display group no. Indicated on display Designation

For development and production purposes

22
only

1 = Learning demand display

23 Read measured value 2 = Min. stop of throttle valve positioner
Adaptation block 23 3 = Emergency running stop of throttle valve
Throttle valve positioner 1234 positioner
4 = Max. stop of throttle valve positioner

1 = Engine speed
24 Read measured value 2 = Engine load
Knock block 24 3 = Ignition angle
control 1234 4 = Sum of ignition angle retardation for
cylinders 1 to 4

1 = Specified load without correction

25 Read measured value 2 = Specified load after correction
Boost pressure block 25 3 = Actual load
control 1234 4 = Duty cycle, boost pressure control
solenoid valve

1 = Idling speed control

26 Read measured value 2 = Idling air mass, learned (no gear
Idling air block 26 engaged on automatic)
demand 1234 3 = Coolant temperature
4 = Engine speed

1 = Load reduction through knock control

27 Read measured value 2 = Engine load after reduction
Load reduction through block 27 3 = Engine speed
knock control 1234 4 = Duty cycle, boost pressure control
solenoid valve

Display group no. Indicated on display Designation

28...94 Not used

 95...97 For development and production purposes only

1 = Voltage, throttle valve potentiometer

98 2 = Voltage, idling positioner potentiometer
Read measured value
Adaptation 3 = Operating status: idling/part throttle
block 98
Throttle valve control 4 = Adaptation status
1234
part Adaptation running, adaptation OK, adaptation
ERROR

1 = Engine speed
99 Read measured value
2 = Coolant temperature
Lambda block 99
3 = Lambda control
control 1234
4 = Lambda control ON

Motronic self-diagnosis
Display groups 00 - 07

Display group 00

Display Specified Equivalent measured

Designation
zone readout value

Coolant temperature (requirement for basic

1 170...204 80...105 oC
setting)

2 1) 32...48 1.6...2.4 ms
Engine load (no consumers switched on)

2 2) 20...55 1.0...2.5 ms

2 3) 10...40 0.5...1.5 ms

3 76...96 720...960 rpm Engine speed (no consumers switched on)

4 176...212 12...14.5 Battery voltage

5 0...12 0...5o Throttle valve angle

Idling speed air mass control value (idling

6 112...144 -4...+4 kg/h
speed control)

7 112...144 -4...+4 kg/h Learned value for idling speed air mass

Control value for mixture formation

(lambda control value)
8 1) 121...137 -5...+5 %
(only relevant in basic setting and after
approx. 1.5 mins)

8 2)3) 115...143 -10...+10 %

1) Engine code ADP 2) Engine code ADR 3)Engine code AEB

 Display Specified Equivalent
Designation
zone readout measured value

243...255 Learned value for mixture formation (lambda

-0.64...
9 or learned value) additive
+0.64%
0...+13 (if outside tolerance, perform test drive)

Learned value for mixture formation (lambda

10 118...138 -8...+8 % learned value) multiplicative (if outside tolerance,
perform test drive)

1) Engine code ADP 2) Engine code ADR 3)Engine code AEB

Notes on Display zones 9 and 10:

 ◆ In the case of the additive learned value the injection time is changed by a fixed amount which
is not dependent on the basic injection time.
 ◆ The multiplicative learned value represents a percentage change in the injection period.

Test table, Display group 00

Display Readout on V.A.G

Cause of fault Fault remedy
zone 1551

- Coolant temperature sender -G62

- Check G62 =>Page
1 higher than 204 - Wiring connection to Motronic control
28-29
unit -J220

- Coolant temperature sender -G62 - Check G62 =>Page

- Wiring connection to Motronic control 28-29
lower than 170
unit -J220 - Check coolant
- Coolant thermostat constantly open thermostat

- Switch off air

conditioner
- Air conditioner switched on
- Switch off electrical
- Electrical consumers on
Greater than the consumers
2 - Lambda control at rich or lean stop
specified value - Check lambda
- Air conditioner compressor running
control
although air conditioner is off
- Check A/C
compressor actuation

- Unmetered air downstream of air

mass meter
Less than specified - Unmetered air downstream of throttle
- Eliminate cause
value valve
- Vacuum hose disconnected
- Fuel pressure regulator

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551
 - Move selector lever to "P" or
"N"
- Gear engaged (autom. gearbox)
Eliminate load (air conditioning
lower than - Engine load from ancillaries
3 system/power
76 - Throttle valve control part -J338
steering/alternator)
sticking or defective
Check throttle valve control
part -J338

- Idling speed switch -F60 not

closed/defective - Interrogate the fault memory
- Large quantity of unmetered air and check/adjust idling switch
higher than
(cannot be compensated by idling Eliminate air leak
96
stabilisation) Check throttle valve control
- Throttle valve control part -J338 part -J338
sticking or defective

- Alternator defective, battery heavily

- Check voltage, charge battery
discharged
Increase engine speed for
- High load on electrical system shortly
several minutes and switch off
after starting engine due to high charge
lower than ancillaries
4 current and load from ancillaries
176 Check power supply to
- Contact resistance in the positive
Motronic control unit =>Page
supply or ground connection for
28-26
Motronic control unit
Eliminate current drain
- Current drain with ignition off

- Voltage control on alternator defective - Check voltage; if necessary,

higher than
- Excess voltage from assisted start or fit a new voltage regulator.
212
high speed charger Interrogate fault memory

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

5 lower than 0 - Not possible _______________________________

- Basic setting of throttle

valve control part not
performed
- Throttle valve
higher than potentiometer in throttle - Perform basic setting of throttle valve
12 valve control part defective control part =>Page
- Throttle cable setting not
OK
- Throttle valve mechanism
sticking

6 - Unmetered air - Eliminate air leak

lower than
and downstream of throttle - Notes on Display group 05,
118
7 valve Display zone 3 => Page 01-77

- Eliminate load, switch off ancillaries

higher than - Increased engine load
- Notes on Display group 05,
128 due to ancillaries
Display zone 3 => Page 01-77

Display Readout on Cause of fault Fault remedy

 zone V.A.G 1551

- Engine running too rich,

lambda control in "lean"
- Depress accelerator briefly at 20
direction
sec intervals until learning procedure
- Large quantity of fuel from
is finished
ACF system (not with basic
8 lower than 121 => Display group 06, Display zone 3
setting)
- Replace vacuum hose
- Leak in vacuum hose for fuel
- Check lambda learned values,
pressure regulator
Display group 08 => Page 01-83
- Lambda learned values at
stop

- Engine running too lean,

lambda control enriches
mixture
higher than - Eliminate air leak
- Unmetered air
137 - Check injection quantity
- Injectors defective
=> Page 01-83
- Lambda learned values at
stop

Readout
fluctuates - Fuel reserve too low
- At least 10 l fuel in tank - Display
or remains - Lambda mixture control is on
group 06, note on Display zone 3
constant at open loop control
128

lower than 243

9 or
- =>Display group 08, Display zones 2 and 3
higher than 13

lower than 118

or
10
higher than - =>Display group 08, Display zones 2 and 3
138

Display group 01, basic function

Specified
Indicated on display Designation
readout

Read measured value block

1 = Engine speed (shown in increments of 40
1 760...960 rpm
rpm)
1234

1) 1.6...2.4 ms
2) 1.0...20.5 ms 2 = Engine load (injection period per revolution)
3) 0.5...1.5 ms

0...5 <o 3 = Throttle valve angle

12 oBTDC 4 = Ignition angle

1) Engine code ADP 2) Engine code ADR 3) Engine code AEB

Test table, Display group 01

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

- Move selector lever to "P" or "N"

- Gear engaged (autom. gearbox)
Eliminate load (air conditioning
Less than - Engine load from ancillaries
1 system/power steering/alternator)
760 rpm - Throttle valve control part -J338
Check throttle valve control part -
sticking or defective
J338

- Idling speed switch -F60 not

closed/defective - Interrogate the fault memory
- Large quantity of unmetered air and check/adjust idling switch
Greater than
(cannot be compensated by idling Eliminate air leak
960 rpm
stabilisation) Check throttle valve control part -
- Throttle valve control part -J338 J338
sticking or defective

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

Less than - Technically not

2 __________________________________
specified value possible*

- Poor idling (not

running on all
cylinders)
- Air mass meter -G70 - Injector or spark plugs defective
defective Interrogate fault memory
- Throttle valve control Check throttle valve control part -J338
Greater than
part -J338 defective =>Page 24-58
specified value
- Electrical consumers Switch off the consumers
on Centre steering wheel
- Steering wheel at full Move selector lever to "P" or "N"
lock
- Gear engaged
(autom. gearbox)

*) Lower values can only occur when vehicle is on overrun.

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

Less than 0
3 - Not possible _________________________________
<o

Greater - Basic setting of throttle - Perform basic setting of throttle valve

than 5 <o valve control part -J338 not control part -J338
 performed
- Throttle valve
potentiometer in throttle
valve control part -J338
defective or incorrectly set
- Throttle cable setting
- Throttle valve mechanism
sticking

- Electrical consumers on
- Switch off the consumers
Lower than - Steering wheel at full lock
4 Centre steering wheel
12oBTDC - Gear engaged (auto.
Move selector lever to "P" or "N"
gearbox)

Greater
than - Not possible __________________________________
12oBTDC

Notes on Display zone 3:

 ◆ When accelerator pedal is fully depressed, the display value is between approx. 85...90 <o.
 ◆ The following fixed substitute value appears as soon as a fault is detected in the throttle valve
potentiometer:

- Engine code ADP: 45 <o

- Engine code ADR: 35 <o

- Engine code AEB: 45 <o

Display group 02, basic function

Specified
Indicated on display Designation
readout

Read measured value

Display zone 1 = engine speed (shown in increments of
block 2 760...960 rpm
40 rpm)
1234

ADP: 1.6..2.4 ms Display zone 2 = theoretical injection period per

ADR: 1.0..2.5 ms crankshaft
AEB: 0.5..1.5 ms revolution (engine load)

ADP: 2.0...3.5
ms
ADR: 2.0...5.0 Display zone 3 = corrected injection period per engine
ms cycle
AEB: 1.5...3.0
ms

ADP: 2.5...4.5 Display zone 4 = intake air mass

g/s
ADR: 2.0...4.0
g/s
AEB: 1.8...4.0
 g/s

Test table, Display group 02

Display zone Readout on V.A.G 1551 Cause of fault Fault remedy

1 - See Display group 01, Display zone 1

2 - See Display group 01, Display zone 2

Note on Display group 2, basic function:

 ◆ Display zone 2 shows the injection period which corresponds to the intake air mass and the
engine load when idling. This value is a purely calculated, theoretical value which, because of the
processor technology, only relates to a single crankshaft revolution. The engine load when idling
is the load created by the internal friction which the engine has to overcome and the power
required to drive the ancillaries. The intake air mass is shown in Display zone 4.
 ◆ Display zone 3, on the other hand, shows the injection period for a complete engine cycle, i.e.
two crankshaft revolutions.
 ◆ However it is the corrected actual injection period which is shown in Display zone 3 and not the
doubled value of Display zone 2. Correction of variables such as:

- Lambda control

- Fuel supply from activated charcoal filter

- Air density, air temperature

- Vehicle voltage (quicker / slower opening of the injectors)

 ◆ For example, if the engine draws in unmetered air, only the calculated
value in Display zone
2 should change (injection period per crankshaft revolution). The lambda control ensures
that the actual injection period per engine cycle remains at the specified value.

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

- Large quantity of fuel from the ACF

Less than - Check solenoid valve for
system
3 specified activated charcoal filter
- Wrong injectors installed (delivery rate
value =>Page 24-22
too high)

- Increased engine load due to electric

Greater than
consumers, air conditioner or engaged
specified - Eliminate load
gear, power-assisted steering at full
value
lock

Less than - Large quantity of unmetered air

4 specified between intake manifold and air mass - Eliminate air leak
value meter
 - Move selector lever to "P" or
Greater than "N"
- Gear engaged (autom. gearbox)
specified Eliminate load (air conditioning
- Engine load from ancillaries
value system/power
steering/alternator)

Display group 03, basic function

Specified
Indicated on display Designation
readout

Read measured value block

1 = Engine speed (shown in increments of 40
3 760...960 rpm
rpm)
1234

12...140.5 V 2 = Battery voltage

80...105 oC 3 = Coolant temperature

...oC 4 = Intake air temperature

Test table, Display group 03

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

1 - See Display group 01, Display zone 1

- Alternator defective, battery heavily - Check voltage, charge

discharged battery
- High load on electrical system shortly Increase engine speed for
after starting engine due to high charge several minutes and switch
Less than 12
2 current and load from ancillaries off ancillaries
V
- Contact resistance in the positive supply Check power supply to
or ground connection for Motronic control Motronic control unit
unit =>Page 28-26
- Current drain with ignition off Eliminate current drain

- Check voltage; if
- Voltage control on alternator defective
Greater than necessary, fit a new voltage
- Excess voltage from assisted start or
14.5 V regulator.
high speed charger
Interrogate fault memory

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

- Engine too cold - Test drive if necessary.

3 Less than 80 oC - Sender for coolant temperature or Check -G62 =>Page 28-
wiring to Motronic control unit 29
 - Radiator dirty - Clean radiator
- Radiator fan not working Check function
Greater than 105
- Coolant thermostat defective Check coolant thermostat
oC
- Sender for coolant temperature or Check -G62 =>Page 28-
wiring to Motronic control unit 29

Constant 19.5 - Fault detected on intake air - Interrogate fault memory

41)
oC temperature sender -G42 - Page 28-41

- Check -G42 =>Page 28-

Greater than 2) - Intake air temperature sender -G42
41

1) - There is no intake air temperature sender installed for vehicles with engine codes ADP and ADR. A
constant value of 19.5 oC is always displayed.

- For vehicles with engine code AEB, the value measured by the intake air temperature sender is
displayed.

2) when vehicle is running, up to 24 oC above ambient temperature

when vehicle is stationary, depending on the heat accumulation in the engine and the standing time, up to
110 oC

Note on Display zone 3:

The Motronic control unit operates with voltages of between 10 and 15 V. However, voltages below 12 V
or above 14.5 V indicate a defect.

Display group 04, idling speed adjustment

Specified
Indicated on display Designation
readout

Read measured value

block 4 0...5 <o 1 = Throttle valve angle
1234

2 = Idling air mass, learned (no gear engaged on

-1.1...5+1.1 g/s
automatic)

3 = Idling air mass, learned, with gear engaged on

-1.7...+1.7 g/s
automatic

Idling 4 = Operating status

Test table, Display group 04

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

1 - See Display Group 01, Display

 zone 3

Greater than -1.1 - Unmetered air downstream of

2 - Eliminate air leak
g/s throttle valve

- Switch off air conditioner and

- Large load from ancillaries
Greater than electrical consumers
- Constriction/foreign matter in
+1.1 g/s - Eliminate constriction or foreign
intake area
body

Note on Display zone 1:

When the accelerator pedal is fully depressed, the display value is between approx. 85...90 <o.

Note on Display zones 2 and 3:

The display shows how far the learned values of the idle stabilisation have "drifted away" from the pre-
programmed mean value. With a new engine, the display will show a positive value because of the
greater friction; if the engine has been run in it will show a negative value. A value of - 1.1 g/s combined
with an excessively low value in Display group 05, Display zone 3, indicates the presence of unmetered
air.

 ◆ The value displayed is not measured by the air mass meter but calculated from information
from the throttle valve potentiometer.
 ◆ On vehicles with a manual gearbox Display zone 3 always displays 0.

Note on Display zone 4:

The following operating statuses are displayed:

 ◆ Idling
 ◆ Part throttle
 ◆ Fullthrottle
 ◆ Overrun
 ◆ Enrichment (full throttle enrichment)

Display group 05, idling stabilisation

Indicated on display Specified readout Designation

Read measured value block 5

820...900 rpm 1 = Engine speed (actual)
1234

860 rpm 2 = Engine speed (specified)

-10...+10 % 3 = Idling speed control

1) 2.5...4.5 g/s
2) 2.0...4.0 g/s 4 = Air mass
3) 1.8...4.0 g/s

1) Engine code ADP 2) Engine code ADR 3) Engine code AEB

Note on Display zone 1:

  ◆ The actual engine speed is displayed in increments of 10 (max. 2550 rpm).
 ◆ Fault cause and fault remedy =>Display group 2, Display zone 1.

Note on Display zone 2:

The specified engine speed set by the Motronic control unit is displayed.

Note on Display zone 3:

During idling, the air mass requirement varies with changing load conditions, even though the engine
speed is constant. The change in air mass during idling is shown as a percentage. As soon as the change
has been compensated by the idle stabilisation learning process, the mean value is restored. The amount
of deviation from the mean value depends on the extent of the load change (e.g. as a result of switching
electrical consumers on or off). The learning process proceeds in small stages each time the idling switch
closes. In the event of a large deviation, several stages are required. To do this, depress the accelerator
pedal briefly in 20 second intervals (brief burst of throttle). Every burst of throttle moves the learning
process along a further step.

The deviation that has "drifted away" then appears in Display group 04, Display zone 2. The idling speed
control values remain outside tolerance if the learned values in Display group 04, Display zone 2 have run
on to the stop.

Stop values:

Engine code ADP: -1.13 or +1.42 g/s

Engine code ADR: -1.70 or +1.70 g/s

Engine code AEB: -1.13 or +1.13 g/s

Note on Display zone 4:

 ◆ The display shows the air mass measured by the air mass meter.
 ◆ Ifthe vehicle is in emergency running mode due to a fault in the throttle valve control part, then
the engine runs without idling stabilisation with an increased idling speed (approx. 110...1300
rpm) caused by the emergency running gap. The air throughput is roughly 4.5...5.5 g/s.

Display group 06, idling stabilisation

Specified
Indicated on display Designation
readout

Read measured value

1 = Engine speed (display in increments of 10; max.
block 6 820...900 rpm
2550 rpm)
1234

-10...+10 % 2 = Idling speed control

1) -5...+5 %
2) -10...+10 % 3 = Lambda control
3) -10...+10 %

12 oBTDC 4 = Ignition angle

1) Engine code ADP 2) Engine code ADR 3) Engine code AEB

Test table, Display group 06

Display zone Readout on V.A.G 1551 Cause of fault Fault remedy

1 - See Display group 01, Display zone 1

2 - See Display group 05, Display zone 3

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

Negative display - engine too rich, consequence:

Lambda control produces leaner mixture - Wait 30 seconds
Positive display ("+" is not displayed) - engine too until the display
Outside lean, consequence: Lambda control produces has stabilised
3 tolerance richer mixture - Eliminate air leak
range - Unmetered air - Check injection
- Injector defective quantity
- Lambda learned values (Display group 00 or 08) =>Page 01-83
at stop

4 - See Display group 01, Display zone 4

Note on Display zone 3:

The display should fluctuate around 0. If a constant value of 0 is displayed then the lambda control has
switched from closed loop to open loop control because a fault is present in the lambda control
=>Interrogate fault memory or check Display group 21, Display zone 4.

Display group 07, lambda control and ACF system

Specified
Indicated on display Designation
readout

Read measured value 1) -5...+5 %

block 7 2) -10...+10 % 1 = Lambda control
1234 3) -10...+10 %

-0.1 ... +1.1 V 2 = Lambda probe voltage

3 = Duty cycle, solenoid valve 1 for activated

0...99
charcoal filter

4 = Lambda correction factor with active tank

0.3...1.2
breather

1) Engine code ADP 2) Engine code ADR 3) Engine code AEB

Note on Display zone 1:

=>Display group 06, Display zone 3

Note on Display zone 2:

The voltage signal for "Mixture rich" (low level of residual oxygen) is between about 0.7 and 1.1 V
(referenced to reference ground).

The voltage signal for "Mixture lean" (high residual oxygen) is between about -0.1..+0.3 V (referenced to
reference earth).

During the transition from "rich" to "lean" and vice versa (λ= 1.0), there is a voltage jump from 0.7...1.1 V
to -0.1...0.3 V or vice versa.

Because of the sharp voltage jump the lambda control cannot maintain a constant ideal mixture
composition of λ= 1.0. The system fluctuates continuously between "slightly too lean" and "slightly too
rich".

Note on Display zone 3:

A duty cycle of 0 means that ACF solenoid valve 1 is closed. At a duty cycle of 99 the solenoid valve is
fully open.

Note on Display zone 4:

 ◆ At a display value of 0.3 the engine is receiving a very rich mixture from the ACF system. - The
lambda control therefore has to reduce the injection quantity to 30%.
 ◆ At a display value of 1.0 the ACF system is either delivering an ideal mixture (no intervention
towards lean or rich required), or the ACF valve is closed (adaptation =>Display group 08,
Display zone 4).

 ◆ If
the value displayed is 1.01 ... 1.2 then the mixture coming from the ACF system is too lean. -
The lambda control therefore has to enrich the mixture.

Motronic self-diagnosis
Display groups 08 - 98

Display group 08, lambda learned values

Display
Indicated on display Designation
range

1) 2.0...3.5
ms
Read measured value
2) 2.0...5.0
block 8 1 = Injection period
ms
1234
3) 1.5...3.0
ms
 1) -10...+10
%
2) -10...+10
2 = Lambda learned value at idling (additive)
%
3) -12...+12
%

1) -8...+8 %
2) -8...+8 %
3) -12...+12 3 = Lambda learned value at part throttle (multiplicative)
%

4 = "TB active" means that ACF solenoid valve 1 is cycled

TB active
(6 min)
or
"λ-adaptation" means thatACF solenoid valve 1 is
λ-adaptation
constantly closed (1 min)

1) Engine code ADP 2) Engine code ADR 3) Engine code AEB

Test table, Display group 08

Display Readout on
Cause of fault Fault remedy
zone V.A.G 1551

1 - See Display group 02, Display zone 3

- Lambda learned values low for idling and

normal for part throttle: Oil dilution possible
(high amount of fuel in the oil)
- Disappears after a drive
- Injector leaking
Low lambda on the motorway or after an
- Fuel pressure too high
3 and 4 learned oil change
- Solenoid valve 1 for activated charcoal
values - Check injectors => Page
filter -N80 is constantly open
01-81
- Air mass meter -G70 defective
- Lambda probe heating defective or
lambda probe dirty

Note on Display zones 2 and 3:

Low values mean that the engine is running too rich, and the lambda control is compensating by leaning
out the mixture.

- Lambda learned values high for idling and less high for
part throttle: unmetered air possible around intake manifold
- Injector clogged - Eliminate cause
High
3 - Display zones 2 and 3 high: Air mass meter -G70 - Check injection
lambda
and defective quantity
learned
4 - Fuel pressure too low (fuel supply) => Page 24-18
values
- Unmetered air between -G70 and throttle valve - Eliminate cause
- Unmetered air at manifold gasket
- Lambda probe heating defective or lambda probe dirty

- Check lambda
probe heating
 =>Page 01-81

Note on Display zones 2 and 3:

 ◆ High learned values mean that the engine is running too lean, and therefore the lambda control
is compensating by enriching the mixture.
 ◆ If there is no voltage in the control unit, all the learned values will be reset.
 ◆ `Additive' means that the impact of the fault decreases as the engine speed increases (e.g.
unmetered air).
 ◆ `Multiplicative' means that the impact of the fault increases as the engine speed increases (e.g.
injector fault).

Note on Display zone 4:

During the λ-adaptation the lambda control "learns" the operating conditions without the deviation due to
the fuel vapours from the activated charcoal filter (ACF valve closed).

Display group 09, lambda learned values

Specified
Indicated on display Designation
readout

Read measured value

1 = Engine speed (display in increments of 10; max.
block 9 820...900 rpm
2550 rpm)
1234

1) -5...+5 %
2) -10...+10 % 2 = Lambda control
3) -10...+10 %

-0.1 ... +1.1 V 3 = Lambda probe voltage

1) -10...+10 %
2) -10...+10 % 4 = Lambda learned value at idling (additive)
3) -12...+12 %

1) Engine code ADP 2) Engine code ADR 3) Engine code AEB

Note on Display zone 1:

=>Display group 01, Display zone 1

Note on Display zone 2:

=>Display group 06, Display zone 3

Note on Display zone 3:

=>Display group 07, Display zone 2

Note on Display zone 4:

=>Display group 08, Display zone 2

Display group 10, tank breather

Display
Indicated on display Designation
range

Read measured value block

1 = Duty cycle, solenoid valve 1 for activated charcoal
10 0...99 %
filter
1234

0.3...1.2 2 = Lambda correction factor with active tank breather

-3...+30 3 = Fill factor of activated charcoal filter

0.00...0.30 4 = ACF purging quantity

Note on Display zone 1:

=>Display group 07, Display zone 3

Note on Display zone 2:

=>Display group 07, Display zone 4

Note on Display zone 3:

At a value of -3 there are no fuel vapours in the ACF canister.

At a value of +30 the ACF canister is completely full of fuel vapours.

Note on Display zone 4:

The display shows the percentage by volume of the activated charcoal filter system referenced to the total
intake volume.

At a value of 0.00 nothing is delivered by the ACF system (solenoid valve closed).

At a value of 0.30, 30 % of the intake air mass comes from the ACF system.

Display group 11, fuel consumption:

This display group can be used to assess the dependency of fuel consumption on engine speed,
engine load and vehicle speed.

Specified
Indicated on display Designation
readout

Read measured value block

1 = Engine speed (shown in increments of 40
11 ....rpm
rpm)
1234

1) 1.6...2.4 ms 2 = Engine load (injection period per revolution)

 2) 1.0...2.5 ms
3) 1.0...2.5 ms

0 km/h 3 = Vehicle speed

1) 0.5...1.1 l/h
2) 0.5...1.5 l/h 4 = Fuel consumption
3) 0.5...1.5 l/h

1) Engine code ADP 2) Engine code ADR 3) Engine code AEB

Notes on Display zone 2:

 ◆ The maximum engine load decreases by about 10 % for every 1000 m above sea level.
 ◆ The maximum engine load also falls by up to 10 % at very high ambient temperatures.

Note on Display zone 4:

The specified readout value only applies to idling without any ancillary loads (autom. gearbox, air
conditioner/heater, alternator, power steering pump)

The values when driving at full throttle should not be less than the following:

at 4000 rpm at 6000 rpm

 ◆ Engine code ADP: 7.0 ms 6.1 ms

ADR: 7.5 ms 6.5 ms
AEB: 6.5 ms 6.0 ms

Display group 12, fuel consumption during idling

Specified
Indicated on display Designation
readout

Read measured value 1 = Engine speed (display in increments of 10; max.

820...900 rpm
block 12 2550 rpm)

1234 12...14.5 V: 2 = Battery voltage

1) 0.5...1.1 l/h
2) 0.5...1.5 l/h 3 = Fuel consumption
3) 0.5...1.5 l/h

12 oBTDC 4 = Ignition angle

1) Engine code ADP 2) Engine code ADR 3) Engine code AEB

Note on Display zone 1:

=>Display group 01, Display zone 1

Note on Display zone 2:

=>Display group 03, Display zone 2

Note on Display zone 3:

=>Display group 11, Display zone 4

Note on Display zone 4:

=>Display group 01, Display zone 4

Display group 13, knock control

Specified
Indicated on display Designation
readout

Read measured value block

1 = Ignition timing retardation by knock control,
13 0...15 oCS
cylinder 1
1234

2 = Ignition timing retardation by knock control,

0...15 oCS
cylinder 2

3 = Ignition timing retardation by knock control,

0...15 oCS
cylinder 3

4 = Ignition timing retardation by knock control,

0...15 oCS
cylinder 4

Notes:

 ◆ Knock control is active over the entire engine speed range from a 3 ms engine load upwards.
When a 3 ms engine load is exceeded the current values for the ignition timing retardation are
displayed. If the load is below this value then the ignition timing retardation is cancelled again.
 ◆ If there is audible knocking but no retardation of the ignition timing then increase the engine
speed to above 3000 rpm for 5 seconds to initiate the knock sensor fault detection (diagnosis).
 ◆ If the ignition timing retardation value differs greatly from one cylinder to the others then the
following faults are possible:
- Loose ancillaries
- Corrosion on the plug connector
- Engine damage (e.g. oil combustion due to a defective piston)
 ◆ If the ignition timing retardation values for all the cylinders are high, the following faults are
possible:
- Corrosion at connector
- Specified torque (20 Nm) not achieved
- Open circuit
- Knock sensor defective
- Loose ancillaries
- Poor fuel quality

Display group 14, knock control

Specified
Indicated on display Designation
readout
 Read measured value block
14 ... rpm 1 = Engine speed (shown in increments of 40 rpm)
1234

... ms 2 = Engine load (injection period per revolution)

3 = Ignition timing retardation by knock control,

0...15 oCS
cylinder 1

4 = Ignition timing retardation by knock control,

0...15 oCS
cylinder 2

Notes:

 ◆ With this display group it is possible to check the ignition timing retardation for cylinders 1 and 2
at specific engine speeds and under specific load conditions.
 ◆ Causes for ignition timing retardation =>Display group 13

Display group 15, knock control

Specified
Indicated on display Designation
readout

Read measured value block

15 ... rpm 1 = Engine speed (shown in increments of 40 rpm)
1234

... ms 2 = Engine load (injection period per revolution)

3 = Ignition timing retardation by knock control,

0...15 oCS
cylinder 3

4 = Ignition timing retardation by knock control,

0...15 oCS
cylinder 4

Notes:

 ◆ With this display group it is possible to check the ignition timing retardation for cylinders 3 and 4
at specific engine speeds and under specific load conditions
 ◆ Causes for ignition timing retardation =>Display group 13

Display group 16, knock control

Indicated on display Specified readout Designation

Read measured value block 16

0.6...1.4 V 1 = Knock sensor signal, cylinder 1
1234

0.6...1.4 V 2 = Knock sensor signal, cylinder 2

 0.6...1.4 V 3 = Knock sensor signal, cylinder 3

0.6...1.4 V 4 = Knock sensor signal, cylinder 4

Notes:

 ◆ If the difference between the highest and lowest knock control signals is more than 50%, this
may be due to corrosion on the connector.
 ◆ If no faults are detected during the electrical testing of the knock sensor, the wiring and the plug
connection, then the engine should be checked for loose ancillaries or engine damage =>Display
group 13.
 ◆ At higher engine speeds, the voltage signal displayed for the knock sensors may reach values
of up to 5.1 V.

Display group 17, distributor basic setting (engine code ADP only)

Specified
Indicated on display Designation
readout

Read measured value block

1 = Engine speed (shown in increments of 40
17 820...900 rpm
rpm)
1234

1.0...2.5 ms 2 = Engine load (injection period per revolution)

-12...+12 oCS 3 = Position of Hall sender signal

12 oCS 4 = Ignition angle

Notes:

The position of the Hall sender is set by rotating the distributor. The Motronic control unit can process the
signal in a range from -12...+12 oCS.

Keep to a range of-3...+3 oCS when adjusting.

Display group 17, CAT heating (engine code ADR1) only)

Specified
Indicated on display Designation
readout

Read measured value block

1 = Engine speed (shown in increments of 40
17 ...rpm
rpm)
1234

... ms 2 = Engine load (injection period per revolution)

0.00...2.00 3 = Energy balance for cat heating

.... oBTDC 4 = Ignition angle

1)With engine code AEB this display group is irrelevant, as the catalytic converter is located so close to
the engine.

Notes:

 ◆ In order to bring the catalytic converter up to operating temperature as quickly as possible after
a cold start, the engine speed is raised to approx. 1200 rpm during idling and the ignition timing is
retarded up to a maximum of 6 oATDC. In the part throttle range only the retardation of the
ignition angle is effective.
 ◆ This function for rapid heating of the catalytic converter is effective at starting temperatures of -
10 to +39 oC.
The function is aborted under the following conditions:
- Engine speed greater than 4000 rpm
- Load above 7.4 ms
- Energy balance above 1.0
- Full throttle for longer than 2 sec.
- Vehicle speed greater than 55 km/h
- A/C on
As soon as the function has been aborted the display for the energy balance stops and is reset
during the next start.
 ◆ The function does not become effective again if the values are below the above criteria.
 ◆ As soon as the energy balance counter reaches the value 1 the catalytic converter is at
operating temperature (at least 120 ml of fuel have been burned). The counter keeps going up to
a value of 2. This display has no relevance.

Display group 18, altitude compensation

Specified
Indicated on display Designation
readout

Read measured value

block 18 ... rpm 1 = Engine speed (shown in increments of 40 rpm)
1234

2 = Engine load without altitude compensation (injection

... ms
period per revolution)

...ms 3 = Engine load after altitude compensation

-30...+25% 4 = Altitude correction factor

Notes:

The Motronic control unit compares the load signal from the air mass meter with a load value calculated
from the throttle valve angle and the engine speed. The difference between the two values is the altitude
correction factor. On AEB engines the altitude compensation is carried out via the altitude sensor. Display
zone 4 therefore always shows 0 %.

The following factors are influenced by the altitude compensation:

 ◆ Determination of starting fuel delivery

 ◆ Acceleration enrichment
 ◆ Lean mixture during deceleration
 ◆ Intake manifold pulsation compensation
No altitude compensation is necessary at altitudes of approx. 400 m above sea level under standard
weather conditions.

- at sea level the correction factor is up to + 5 %.

- at an altitude of 2000 m the correction factor is approx. +20 %.

- the correction factor can vary significantly depending on the weather conditions.

Display group 19, torque reduction (vehicles with automatic gearbox only)

Indicated on display Display range Designation

Read measured value block 19

...rpm 1 = Engine speed (shown in increments of 40 rpm)
1234

... ms 2 = Engine load

... oCS 3 = Retardation of ignition angle

... oCS 4 = Ignition angle

Notes:

 ◆ This display group can be used to assess how the ignition timing retardation reduces the engine
torque on changing gear and thus makes gear shifts smoother.
 ◆ Because of the brief signal, the V.A.G 1551 does not always recognise the ignition timing
retardation.

Display group 20, operating states

Indicated on display Display Designation

Read measured value block

1 = Engine speed (display in increments of 10; max.
20 ... rpm
2550 rpm)
1234

Neutral
2 = Selector lever position: neutral or gear engaged
Gear ENG.

3 = Air conditioner
A/C high
High = high heating or cooling output
A/C low
Low = low heating or cooling output

Compr. OFF
Compr. 4 = A/C compressor OFF/ON
ENG.

Note on Display zone 2:

On vehicles with a manual gearbox the display always reads "Gear ENG".

Note on Display zone 3:

On vehicles without air conditioner the display shows "A/C high" when the rear window heating is
switched on.

Note on Display zone 4:

Vehicles without air conditioner always show "Compr. OFF".

Display group 21, operating status of lambda control

Indicated on display Display range Designation

Read measured value block 21

... rpm 1 = Engine speed (shown in increments of 40 rpm)
1234

... ms 2 = Engine load

... oC 3 = Coolant temperature

λ- control OFF
4 = Lambda control ON/OFF
λ- control ON

Notes:

At starting temperatures below +5 oC the lambda control is not released by the Motronic control unit until
a coolant temperature of +5 oC is reached.

At starting temperatures above +5 oC the lambda control does not start until a signal voltage is detected.

When the lambda control is switched off, the engine runs according to the map stored in the control unit.

Display group 22

This Display group is only intended for development and production.

The values shown have no relevance for fault finding in the workshop.

Display group 23, adaptation of throttle valve control part

Specified
Indicated on display Designation
readout

Read measured value

100000 0 . . . . . = Throttle valve potentiometer adjustment with
block 23

1234 Potentiometer for idling adjuster not OK

 . 1 . . . . = No relevance or not possible

. . 1 . . . = Learning process max stop of throttle valve

potentiometer not OK.

. . . 1 . . = Learning process min. stop of throttle valve

potentiometer not OK.

. . . . 1 . = Learning process max. stop of potentiometer

for

idling adjuster not OK

. . . . . = Learning process min. stop of potentiometer for

idling adjuster not OK

70...93 % Display zone 2 = min. stop of throttle valve positioner

Display zone 3 = emergency running stop of throttle

67...83 %
valve positioner

08...39 % Display zone 4 = max. stop of throttle valve positioner

Note:

6 digits appear in Display zone 1

Note on Display zone 1:

If the specified readout value is not achieved: Perform basic setting of throttle valve control part =>Page
24-59

Note on Display zones 2, 3 and 4:

Display shows stop values learnt during last basic setting..

Note on Display zones 1, 2, 3 and 4:

If specified display value is still not attained after performing basic setting, check wiring for open
circuit/short circuit and connectors for dirt/corrosion before renewing throttle valve control part.

Display group 24, knock control

Specified
Indicated on display Designation
readout

Read measured value block

24 ... rpm 1 = Engine speed (shown in increments of 40 rpm)
1234
 ... ms 2 = Engine load

... oBTDC 3 = Ignition angle

4 = Sum of ignition angle retardation for cylinders

... oCS
1 to 4

Notes:

The knock control must retard the ignition timing as soon as knocking is detected in order to prevent
damage to the engine.

However, the ignition timing retardation increases the exhaust gas temperature. There is a risk of
overheating for the catalytic converter and on the AEB engine, also for the turbocharger.

An ignition timing retardation of for example 3 oCS on all cylinders has exactly the same effect as an
ignition timing retardation of 12oCS on a single cylinder.

To avoid overheating, a richer mixture is supplied when the total ignition timing retardation exceeds
approx. 10 oCS at full throttle

From a total ignition timing retardation of approx. 24 oCS the boost pressure is also reduced on the AEB
engine.

Display group 25, boost pressure control (engine code AEB only)

Specified
Indicated on display Designation
readout

Read measured value block

25 3.0...8.0 ms 1 = Specified load without correction
1234

3.0...8.0 ms 2 = Specified load after correction

0.5...8.0 ms 3 = Actual load

4 = Duty cycle, boost pressure control solenoid

0...99 %
valve

Notes:

 ◆ This display group should only be assessed at full throttle.

 ◆ The driver sets the specified load through the position of the accelerator pedal (display zone 1).
The specified load is reduced by the following correction factors:
- Total ignition timing retardation through knock control above 24 oCS
- Altitude compensation (map-dependent)
- Coolant temperature above 105oC
The boost pressure control limits the load to the specified load after correction.
 ◆ If the actual load deviates from the specified load by more than 0.5 ms (Display zone 2 or 3)
then there is a fault in the boost pressure control.
 ◆ As soon as the Motronic control unit detects a difference of more than 1 ms, a fault is stored in
the boost pressure control and the boost control solenoid valve is actuated with a fixed duty cycle
 of 5 %.

Display group 26, idling air demand (engine code AEB only)

Specified
Indicated on display Designation
readout

Read measured value

block 26 -10%...+10 % 1 = Idling speed control
1234

2 = Idling air mass, learned (no gear engaged on

-1.1...+1.1 g/s
automatic)

80...105 oC 3 = Coolant temperature

760...960 rpm 4 = Engine speed (shown in increments of 40 rpm)

Note on Display zone 1:

=>Display group 05, Display zone 3

Note on Display zone 2:

=>Display group 04, Display zone 2

Note on Display zone 3:

=>Display group 03, Display zone 3

Note on Display zone 4:

=>Display group 01, Display zone 1

Display group 27, load reduction through knock control (engine code AEB only)

Specified
Indicated on display Designation
readout

Read measured value block

27 0...5ms 1 = Load reduction through knock control
1234

0.5...0.8 ms 2 = Engine load after reduction

3 = Engine speed (shown in increments of 40

... rpm
rpm)

4 = Duty cycle, boost pressure control solenoid

0...99 %
valve

Notes:
The boost pressure is reduced in order to limit the engine load.

The load is determined from the air mass meter signal.

If the sum of engine load plus load reduction reaches or exceeds a value of 8, this indicates a fault in the
area of the air mass meter.

Display group 98, throttle valve control part

Indicated on display Specified readout Designation

Read measured value block 98

...V 1 = Voltage, throttle valve potentiometer
1234

... V 2 = Voltage, idling positioner potentiometer

Idling
3 = Operating status
Part throttle

ADP running
ADP OK 4 = Adaptation status
ADP ERROR

Note on Display zone 4:

ADP = Adaptation =>check throttle valve control part=>Page 24-58.