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Self-diagnosis for the Motronic system
Reading measured value block: Display Groups 00 to 10
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Display group 00 (decimal values)
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▪ Engine running at idling speed
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Display zones
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Specified value
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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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Learned value for mixture formation
(if outside tolerance, perform test drive)
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118...138
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-8...+8 %
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Learned value for mixture formation
(if outside tolerance, perform test drive)
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115...141
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-0.64...+0.64 %
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Control value for mixture formation
(if outside tolerance, perform test drive)
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78...178
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-10...+10 %
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Learned value for idle stabilisation
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120...136
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-4.0...+4.0 kg/h
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Control value for idle stabilisation
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122...134
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-3.0...+3.0 kg/h
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Throttle angle
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0...12
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0...5 °
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Battery voltage
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142...206
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10...14.5 V
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Engine speed (idling speed)
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80...92
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800...920 rpm1)
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Engine load (no consumers)
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10...30
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0.5...1.5 ms
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Coolant temperature (pre-condition for basic setting)
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170...204
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80...105 °C
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1) Current values:
=> Exhaust Emissions Check binder
Test table, Display Group 00
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Display zone
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Readout on V.A.G 1551
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Cause of fault
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Fault remedy
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1
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greater than 204
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- -G62 sensor for coolant temperature
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- Check -G62
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- Wiring to engine control unit
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less than 170
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- -G62 sensor for coolant temperature
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- Check -G62 => Page 28-17
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- Wiring to engine control unit
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- Coolant thermostat constantly open
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- Check coolant thermostat
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Display zone
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Readout on V.A.G 1551
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Cause of fault
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Fault remedy
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2
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greater than 30
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- Air conditioning system switched on
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- Switch off the air conditioner
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- Electrical consumers on
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- Switch off the consumers
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- Lambda control at rich or lean stop
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- Check the lambda control
=> Page 24-48
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- Air conditioner compressor running although air conditioner is off
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- Check air conditioner compressor control => Page 24-95
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less than 10
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- Unmetered air downstream of air mass meter
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- Rectify fault
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- Unmetered air downstream of throttle valve
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- Vacuum hose disconnected
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- Fuel pressure regulator
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Display zone
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Readout on V.A.G 1551
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Cause of fault
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Fault remedy
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3
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less than 80
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- Drive position engaged (automatic gearbox)
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- Put selector lever in P or N position
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- Engine loaded by ancillaries
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- Remove load (e.g. air conditioner, power steering)
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- -J338 throttle valve control unit sticking or defective
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- Check J338 throttle valve control unit
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greater than 92
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- -F60 idling switch open or defective
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- Interrogate the fault memory and check/adjust idling switch
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- Large quantity of unmetered air (cannot be compensated by idling speed stabiliser )
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- Rectify unmetered air
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- -J338 throttle valve control unit sticking or defective
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- Check -J338 throttle valve control unit
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Display zone
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Readout on V.A.G 1551
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Cause of fault
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Fault remedy
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4
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less than 142
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- Alternator defective, battery heavily discharged
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- Test voltage, charge battery
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- Heavy high load on electrical system shortly after starting engine due to high charging current and load from ancillaries
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- Slightly increase engine speed for several minutes and switch off ancillaries
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- Contact resistance in positive supply or earth connection for engine control unit
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- Check power supply to engine control unit
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- Current drain with ignition off
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- Rectify current drain
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greater than 206
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- Voltage regulator on alternator defective
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- Test voltage; if necessary replace regulator
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- Excess voltage from assisted start or high speed charging
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- Interrogate the fault memory
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Display zone
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Readout on V.A.G 1551
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Cause of fault
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Fault remedy
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5
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less than 0
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- Not possible
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greater than 12
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- Basic setting of throttle valve control unit not performed
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- Perform basic setting of throttle valve control unit
=> Page 01-7
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- Throttle control cable not OK
- Throttle valve potentiometer in throttle valve control unit defective
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- Adjust throttle cable
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- Throttle valve mechanism sticking
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- Rectify fault, replace if necessary
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6
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less than 122
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- Unmetered air downstream of throttle valve
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- Eliminate unmetered air
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greater than 134
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- Increased engine load from ancillaries
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- Remove load by switching off ancillaries
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Display zone
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Readout on V.A.G 1551
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Cause of fault
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Fault remedy
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7
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less than 120
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- Unmetered air downstream of throttle valve
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- Eliminate unmetered air
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greater than 136
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- Increased engine load from ancillaries
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- Reduce load by switching off ancillaries
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8
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less than 78
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- Mixture too rich; lambda control makes it leaner
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- Press down on accelerator pedal at 20 second intervals until the learning process has been performed
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- Large quantity of fuel from ACF system (not with basic setting)
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- Leak in vacuum hose for fuel pressure regulator
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- Replace vacuum hose
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- Lambda learned values at stop
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- Check lambda-learned values, Display Group 08
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Display zone
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Readout on V.A.G 1551
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Cause of fault
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Fault remedy
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8
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greater than 178
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- Mixture too lean; lambda control makes it richer
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- Check injection quantity
=> Page 24-19
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- Unmetered air
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- Eliminate unmetered air
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- Injectors defective
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- Lambda learned values at stop
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- Check lambda-learned values, Display Group 08
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Readout fluctuates
or remains
constant at 128
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- Fuel reserve too low
- Lambda mixture control is on open loop control
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- At least 10 l of fuel in the tank
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9
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less than 115
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greater than 141
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- Display Group 08, display panels 2 and 3
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10
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less than 118
or
greater than 138
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- Display Group 08, display panels 2 and 3
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Display Group 01 - Basic function at idling speed (engine warm, coolant temperature not below +85 °C):
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Read measured value block 1
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⇒
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◂ Display readout
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800...920 rpm
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0.5...1.5 ms
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0...5 <°
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3...12 °
BTDC
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Ignition timing
▪ 3...12.0°BTDC OK
▪ greater than 12.0°BTDC: Engine loaded => Switch off consumers
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Throttle angle
▪ 0...5 <°: OK.
▪ greater than 5 <°: No throttle valve control unit adaptation => Page 24-62 Throttle cable incorrectly set => Adjust
▪ Throttle valve control unit defective => Replace
Note: The value displayed when the accelerator pedal is fully depressed is around 80...90 <°.
As soon as a fault from the throttle valve potentiometer is recognised, a constant substitute value of 35 <°is displayed.
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Engine load
▪ 0.5...1.5 ms: OK
▪ less than 0.5 ms: Unmetered air downstream of air mass meter => Check intake system
▪ Fuel pressure too high => check - Page 24-15
▪ greater than 1.50 ms Engine loaded => Switch off consumers
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Engine load shown in increments of 40
▪ 800...920 rpm: OK
▪ Outside tolerance: Check idling speed => Page 24-12
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Display Group 02 - Basic function at idling speed (engine warm, coolant temperature not below +85°C):
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Read measured value block 2
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◂ Display readout
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800...920
rpm
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0.5...1.5
ms
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1...3
ms
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1.8...4.0
g/s
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Intake air mass
▪ 1.8...4.0 g/s: OK
▪ less than 1.8 g/s Unmetered air downstream of air mass meter => Check
▪ greater than 4.0 g/s Engine loaded => Switch off consumers
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Corrected injection period per engine cycle
▪ 1.00...3.00 ms: OK
▪ less than 1.00 ms: High proportion from tank breather system => Page 24-57
▪ greater than 3.00 ms: Engine loaded => Switch off consumers
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Engine load, theoretical injection period per crankshaft revolution
▪ 0.5...1.50 ms: OK
▪ less than 0.5 ms: Unmetered air downstream of air mass meter => Check intake system
▪ or fuel pressure too high => Check - Page 24-15
▪ greater than 1.50 ms Engine loaded => Switch off consumers
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Idling speed is shown in increments of 40
▪ 800...920 rpm: OK
▪ Outside tolerance: Check idling speed => Page 24-12
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Notes on Display Group 02:
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◆ Display zone 2 shows the injection period corresponding to the intake air mass and the engine load when idling. This value is a 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.
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◆ Display zone 3, on the other hand, shows the injection period for a complete engine cycle, i.e. two crankshaft revolutions.
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◆ However, the value shown in display zone 3 is not approximately twice the value in display zone 2, but a corrected actual injection period. Corrected by influencing variables such as:
- Lambda control
- Fuel intake from the activated carbon canister
- Air density, air temperature
- Vehicle voltage (faster /slower opening of injectors)
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◆ For example, if the engine takes in unmetered air, only the calculated value in display zone 2 (injection period per crankshaft revolution) should change. The lambda mixture control will ensure that the actual injection period per complete engine cycle remains at the specified value.
Display Group 03; basic function (warm engine, coolant temperature not less than +85 °C)
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Read measured value block 3
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◂ Display readout
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800...920
rpm
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10...14.5
V
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80...105
°C
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...
°C
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Intake air temperature
▪ In the event of an open circuit, a constant temperature of -19.5°C will be displayed as a substitute value.
▪ Check the -G42 sensor for intake air temperature
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Coolant temperature
▪ 80...105 °C: OK
▪ less than 80 °C run engine until warm
▪ Check -G62 sensor for coolant temperature
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Battery voltage
▪ 10.000...14.500 V: OK
▪ Outside tolerance: Check voltage supply from engine control unit => Page 28-19
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Idling speed is shown in increments of 40
▪ 800...920 rpm: OK
▪ Outside tolerance: Check idling speed => Page 24-12
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Note on display zone 4:
It is not possible to give specified values as the display readout is heavily affected by the ambient temperature.
Display Group 04: Idling speed setting (warm engine, coolant temperature not less than +85 °C)
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Read measured value block 4
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◂ Display readout
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0...5
<°
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-1.1...+1.1
g/s
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-1.1...+1.1
g/s
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Idling speed
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Operating status (idling, part load, enrichment, overrun)
▪ Idling: OK
▪ Other display: Check idling speed => Page 24-68
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Idling speed air mass, learned with automatic gearbox with gear engaged D/1/2/3
On cars with manual gearboxes, the display will always show the value "0".
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Idling speed air mass learned (no gear engaged with automatic gearbox)
▪ - 1.1...+ 1.1 g/s: OK
▪ Less than - 1.1 g/s: Unmetered air downstream of throttle valve => Check
▪ higher than + 1.1 g/s: Engine loaded => Switch off consumers
▪ Intake system blocked => Check
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Throttle angle
▪ 0...5<°: OK.
▪ greater than 5 <°: Throttle cable incorrectly adjusted => Adjust
▪ no adaptation, check throttle valve control unit => Page 24-62
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Notes on display zones 2 and 3:
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◆ 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 - 1.7 g/s combined with an excessively low value in Display Group 05, display zone 3, indicates the presence of unmetered air.
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◆ The value displayed is not measured by the air mass meter but calculated from information from the throttle valve potentiometer.
Display Group 05, idling speeding stabilisation when idling: (warm engine, coolant temp. not less than +85 °C)
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Read measured value block 5
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◂ Display readout
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800...920
rpm
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rpm
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-10...+10
%
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1.8...4.0
g/s
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Air mass
▪ 1.8...4.0 g/s: OK
▪ less than 1.8 g/s Unmetered air downstream of air mass meter => Check
▪ greater than 4.0 g/s Engine loaded => Switch off consumers
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Idling speed control
▪ -10...+10 %: OK
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Engine speed (specified)
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Engine speed (actual) is shown in increments of 10
▪ 800...920 rpm: OK
▪ Outside tolerance: Check idling speed => Page 24-12
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Notes on display zone 3:
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◆ During idling, the air mass requirement varies with changing load conditions, even though the engine speed is constant.
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◆ 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).
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◆ 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, the accelerator pedal should be briefly pressed. at intervals of approx. 20 seconds (throttle burst). Each time this is done, a further stage of the learning process is performed.
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◆ The "drifted" deviation then appears in Display Group 04, display zone 2. The values from the idling speed control remain outside the tolerance if the learned values in Display Group 04, display zone 2 have reached the stop (stop values: -:1.1 g/s and +1.1 g/s).
Notes on display zone 4:
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◆ With fault (00670), throttle valve positioner: constant engine speed and air throughput of 2.8 g/s.
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◆ With faults (00670/16505/16506/16507), throttle valve positioner and throttle valve potentiometer, the digital idle stabilisation (DIS) is switched off and a constant speed of approx. 1000 rpm and an air mass of 2.8 g/s is output.
Display Group 06, idling speeding stabilisation when idling: (warm engine, coolant temp. not less than +85°C)
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Read measured value block 6
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◂ Display readout
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800...920
rpm
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-10...+10
%
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-10...+10
%
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3...12°BTDC
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Ignition timing
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Lambda control
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Idling speed control
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Idling speed is shown in increments of 10
▪ 800...920 rpm: OK
▪ Outside tolerance: Check idling speed => Page 24-12
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Notes on display zone 3:
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◆ The display must fluctuate around zero. If a constant 0 is displayed, the lambda control has switched from closed-loop control to open-loop control because there is a fault in the lambda control: Interrogate the fault memory => Page 01-7.
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◆ Operating status of lambda control Display Group 21, display panel 4 .
Display Group 07, lambda control and ACF system: (warm engine, coolant temperature not less than +85 °C)
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Read measured value block 7
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⇒
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◂ Display readout
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-10...+10
%
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0...1
V
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0...99
%
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0.3...1.2
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Lambda correction factor with active fuel tank breather system
▪ less than 1.00 Tank breather supplying rich mixture, lambda control reduces the quantity injected
▪ Display 1.00: No fuel tank breather function or fuel tank breather supplying ideal mixture (λ = 1)
▪ Greater than 1.00 Tank breather supplying lean mixture, lambda control increases the quantity injected
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Signal ratio for -N80 solenoid valve 1 for activated carbon canister
▪ Signal ratio 0 % means -N80 is closed
▪ Signal ratio 99 % means -N80 is fully open
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Lambda probe voltage
▪ Voltage constantly fluctuates back and forth between - 0.1 V and 1.0 V: OK
▪ -0.1...+ 0.3 V: Large amount of residual oxygen, mixture too lean
▪ 0.7...1.0 V: Small amount of residual oxygen, mixture too rich
▪ constant 0.45...0.50 V: Lambda probe not functioning
▪ => Check lambda control - Page 24-44
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Lambda control
▪ -10...+10 %: OK
▪ Outside tolerance: Check lambda control => Page 24-44
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