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Self-odiagnosis
Reading measured value block: Display Groups 00 (block of ten) to 10
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Display group 00 (decimal displayed value)
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▪ Engine running at idling speed
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Display zones
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Specification
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Corresponds to
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1
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2
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3
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4
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5
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6
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7
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8
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9
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10
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Engine speed (idling speed)
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23...27
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760...880 rpm1)
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Injection period
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2...4
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2...4.1 ms
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Throttle valve angle
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4...12
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2...6 <°
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Operating status of lambda control
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see measured value block 99 2)
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Injection period (additive learned value) for lambda control
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0...100
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-0.8...+0.8 ms
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Lambda probe voltage
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0...50
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0.0...1.0 V
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Intake air mass
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14...30
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76...164 mg/stroke
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Coolant temperature
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170...211
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80...110 °C
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Engine control unit power supply voltage
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98...147
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10...15 V
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Intake air temperature
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84...158
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15...71 °C
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1) Up-to-date specifications:
=> Exhaust emissions test binder
2) Display zone 7 gives a decimal figure indicating the operating status of the lambda control. The operating status of the lambda control is represented by an 8 digit bit sequence in Display Group 99, display zone 4 .
Interpreting display group 00
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Display zone: 1 Intake air temperature
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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lower than 84 1)
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- Intake air temperature sender
- Wiring for intake air temperature sender
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- Check intake air temperature sender .
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higher than 158 1)
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Display zone: 2 Engine control unit power supply voltage
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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lower than 98
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- Alternator defective, battery heavily discharged
- High load on electrical system shortly after starting engine due to high charge current and load from ancillaries
- Contact resistance in power supply or earth connection for engine control unit
- Current drain with ignition off
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- Test voltage, charge battery
Increase engine speed for several minutes and switch off ancillaries
Test power supply to engine control unit=> Page 28-23.
Eliminate current drain
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higher than 147
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- Voltage control on alternator defective
- Excess voltage from assisted start or high speed charging
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- Test voltage; if necessary, fit a new voltage regulator.
Interrogate fault memory
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1) Depends upon ambient temperature and length of time vehicle is parked.
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Display zone: 3 Coolant temperature
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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lower than 170
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- Engine too cold
- Coolant temperature sender or wiring to engine control unit
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- Test drive if necessary.
Test coolant temperature sender -G62=> Page 28-20.
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higher than 211
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- Radiator dirty
- Radiator fan not working
- Coolant thermostat defective
- Coolant temperature sender or wiring to engine control unit
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- Clean radiator
Check operation of radiator fan
Test thermostat
Test coolant temperature sender -G62=> Page 28-20.
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Display zone: 4 Intake air mass
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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lower than 14
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- Large quantity of unmetered air between intake manifold and air mass meter
- Air mass meter or wiring to engine control unit
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- Eliminate air leak
Test air mass meter
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higher than 30
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- Drive position engaged (automatic gearbox)
- Engine load from ancillaries
- Air mass meter or wiring to engine control unit
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- Move selector lever to P or N
Remove load (power assisted steering) or switch off ancillaries (e.g. air conditioner)
Test air mass meter
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Display zone: 5 Lambda probe voltage
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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Readout not alternating
(lambda control at rich or lean stop limit; see Display Group 99)
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- Large quantity of unmetered air
- Defective spark plug
- Fuel system pressure too high or too low
- Injector defective
- Coolant temperature sender -G62
- Solenoid valve 1 for activated charcoal filter -N80
- Lambda probe heating not functioning
- Lambda probe defective or dirty
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- Eliminate source of air leak
Test spark plugs
Test fuel pressure regulator and holding pressure .
Read measured value block, Display Group 99
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Display zone: 5 Lambda probe voltage
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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constant 255
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- Short to positive through:
- Lambda probe -G39 or
- Signal wire or
- Engine control unit
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- Test lambda probe .
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constant 80
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- Open circuit through:
- Lambda probe -G39 or
- Signal wire or
- Engine control unit
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- Test lambda probe .
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constant 0
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- Short to earth through:
- Lambda probe -G39 or
- Signal wire
- Engine control unit
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- Test lambda probe .
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Display zone: 6 Injection period (additive learned value) for lambda control (see also Display Group 11)
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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Low lambda learned values
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- Lambda learned values low for idling and normal for part throttle: oil may be diluted (high petrol content in oil)
- Injector(s) leaking
- Fuel pressure too high
- Solenoid valve 1 for activated charcoal filter -N80 is constantly open
- Air mass meter -G70 defective
- Lambda probe heating defective or lambda probe dirty
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- Problem eliminated after motorway drive or oil change
See Display Group 11, display zones 2 and 3
Test injectors .
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Display zone: 6 Injection period (additive learned value) for lambda control
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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High lambda learned values
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- Lambda learned values high for idling and less high for part throttle: unmetered air possible around intake manifold
- Injector blocked
- Fuel pressure too low
- Unmetered air between -G70 and throttle valve
- Unmetered air at manifold gasket
- Lambda probe heating defective or lambda probe dirty
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- Eliminate fault
See Display Group 11, display zones 2 and 3
Test injection quantity .
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Display zone: 7 Operating status of lambda control
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- The operating status of the lambda control is represented by a bit sequence (8 digit number block) in Display Group 99, display zone 4.
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Display zone: 8 Throttle valve angle
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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lower than 4
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- Throttle valve potentiometer in throttle valve control unit -J338 defective or incorrectly adjusted
- Unmetered air between intake manifold and air mass meter (resulting in increased idling speed; the throttle valve control unit will try to regulate the idling speed back to the specified level)
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- Test throttle valve control unit -J338 .
Eliminate sources of air leak
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higher than 12
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- Adaptation of throttle valve control unit -J338 not performed
- Throttle valve potentiometer in throttle valve control unit -J338 defective or incorrectly adjusted
- Throttle cable incorrectly adjusted
- Throttle valve sticking
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- Perform adaptation of throttle valve control unit -J338
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Display zone: 9 Injection period
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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lower than 2
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- Large quantity of fuel from the ACF system
- Wrong injectors installed (delivery rate too high)
- Fuel pressure regulator defective
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- Test solenoid valve for activated charcoal filter .
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higher than 4
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- Increased engine load due to electrical consumers, air conditioner switched on, gear engaged, power assisted steering on full lock
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- Remove load
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Display zone: 10 Engine speed (idling speed)
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V.A.G 1551 readout
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Possible cause of fault
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Fault rectification
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lower than 23
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- Throttle valve control unit -J338 jamming or defective
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- Test throttle valve control unit
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higher than 27
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- Throttle valve control unit -J338 jamming or defective
- Large quantity of unmetered air (idling speed stabilisation can no longer compensate)
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- Test throttle valve control unit
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Eliminate air leak
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Display Group 01: Basic values
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Read measured value block 1
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⇒
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◂ Display readout
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760...880
rpm
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80...110
°C
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0.00...1.00
V
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00000X10
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Throttle valve adaptation requirements (see next Page) 1)
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Lambda probe voltage - see Display Group 00
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Coolant temperature - see Display Group 00
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Engine speed (idling speed) - see Display Group 00
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1) The space marked with an "X" may contain either a 0 or a 1.
Note on display zone 4:
Relevance of figures in 8 digit number block for throttle valve adaptation requirements:
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x
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x
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x
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x
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x
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x
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x
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x
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"1" signifies:
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1
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Fault identified by self-diagnosis 2)
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1
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Signal from automatic gearbox
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1
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A/C compressor switched on
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1
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Idling switch open 1)
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1
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Fault in lambda control
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1
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Throttle valve open (angle check) 1)
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1
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Engine running 1)
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1
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Coolant temperature less than 80 °C
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1) A figure "1" in this position means it will not be possible to perform an adaptation of the throttle valve control unit.
2) The self diagnosis has identified a fault which may not yet have been recorded in the fault memory. If the self diagnosis has identified a fault relating to the throttle valve control unit it will not be possible to perform an adaptation of the throttle valve control unit using the "Basic setting" function.
Display Group 02: Basic values
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Read measured value block 2
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⇒
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◂ Display readout
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760...880
rpm
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76...164
mg/stroke
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0
km/h
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0100
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Operating status of engine
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Road speed
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Intake air mass - see Display Group 00
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Engine speed (idling speed) - see Display Group 00
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Note on display zone 4:
Significance of figures in 4 digit number block for operating status of engine:
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"1" signifies:
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x
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x
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x
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x
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Operating status of engine
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1
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Overrun
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1
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Idling
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1
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Part throttle
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1
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Full throttle
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Display Group 03: Basic values
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Read measured value block 3
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⇒
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◂ Display readout
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760...880
rpm
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76...164
mg/stroke
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2...6
<°
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-100...+100
%
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Signal ratio of throttle valve positioner
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Throttle valve angle - see Display Group 00
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Intake air mass - see Display Group 00
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Engine speed (idling speed) - see Display Group 00
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Display Group 04: Basic values
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Read measured value block 4
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⇒
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◂ Display readout
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760...880
rpm
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76...164
mg/stroke
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2...5
ms
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1.8...4.2
g/s
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Intake air mass
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Injection period - see Display Group 00
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Intake air mass - see Display Group 00
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Engine speed (idling speed) - see Display Group 00
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Display Group 05: Basic values
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Read measured value block 5
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⇒
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◂ Display readout
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760...880
rpm
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10...15
V
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80...110
°C
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15...71
°C
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Intake air temperature - see Display Group 00
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Coolant temperature - see Display Group 00
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Engine control unit power supply voltage - see Display Group 00
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Engine speed (idling speed)
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Display Group 06: Altitude adaptation
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Read measured value block 6
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⇒
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◂ Display readout
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760...880
rpm
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76...164
mg/stroke
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2...6
<°
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0.7...1.3
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Altitude correction factor
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Throttle valve angle
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Intake air mass - see Display Group 00
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Engine speed (idling speed) - see Display Group 00
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Display Group 07: Idling speed setting
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Read measured value block 07
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⇒
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◂ Display readout
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2...6
<°
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x.xx
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x.xx
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0100
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Operating status of engine
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Idling speed learned value (with gear engaged)
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Idling speed learned value (without gear engaged)
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Throttle valve angle
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Note on display zone 4:
Significance of figures in 4 digit number block for operating status of engine:
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"1" signifies:
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x
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x
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x
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x
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Operating status of engine
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1
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Overrun
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1
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Idling
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1
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Part throttle
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1
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Full throttle
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Note:
Measured value block 7 is for information only and has no relevance for fault finding in the workshop.
Display Group 08: Idling speed stabilisation
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Read measured value block 08
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⇒
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◂ Display readout
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760...880
rpm
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800...840
rpm
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-10...+15
%
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1.8...4.2
g/s
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Intake air mass
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Idling speed control
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Specified idling speed when vehicle is stationary
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Engine speed (idling speed) - see Display Group 00
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Display Group 09: Idling speed air requirement
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Read measured value block 9
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⇒
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◂ Display readout
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-10...+15
%
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0000
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80...110
°C
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760...880
rpm
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Engine speed
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Coolant temperature
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Throttle valve control unit adaptation status
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Idling speed control
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Note on display zone 2:
Relevance of figures in 4 digit number block for adaptation status of throttle valve control unit:
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"1" signifies:
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x
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x
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x
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x
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Adaptation status
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1
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A fault has occurred during the adaptation of the throttle valve (interrogate fault memory
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1
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No current in throttle valve control unit (signal ratio = 0)
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1
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Adaptation interrupted due to the battery voltage being too low (below 8V).
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1
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Idling switch open (switch position check)
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Display Group 10: Lambda control and ACF system
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Read measured value block 10
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⇒
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◂ Display readout
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-25...25
%
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0.00...1.00
V
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xxx
%
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xxx
%
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Lambda correction factor with active fuel tank breather system
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Signal ratio of solenoid valve 1 for activated charcoal filter -N80
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Lambda probe voltage
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Lambda control
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Note:
Measured value block 10 is for information only and has no relevance for fault finding in the workshop.
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