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Self-diagnosis
Evaluating measured value blocks, engine codes AFN, AVG
Display group 000 at idling speed (engine warm, coolant temperature not below 80 °C)
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Display group 000 (decimal displayed value)
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▪ Engine running at idling speed
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Read measured value block 0
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◂ Indicated on display
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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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x
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x
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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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◂ Display zones
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Specification
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Corresponds to
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Air mass1)
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69...135
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230...450 mg/H
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Fuel temperature
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91...201
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20...80°C
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Intake manifold temperature
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182...50
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10...100°C
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Coolant temperature
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80...35
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80...110°C
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Atmospheric pressure
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Not relevant
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---
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Intake manifold pressure
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Not relevant
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---
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Injected quantity
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11...45
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2.2...9 mg/H
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Accelerator pedal position
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0
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0 %
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Commencement of injection
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0...88
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3°ATDC...4°BTDC
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Engine speed
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40...432)
38...413)
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840...903 rpm2)
800...860 rpm3)
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1) The measured values are only valid when the exhaust gas recirculation (EGR) is switched on. The EGR is switched off after approx. 3 minutes at idling speed, therefore give burst on throttle or restart engine.
2) Vehicles with manual gearbox
3) Vehicles with automatic gearbox
Display group 001 at idling speed (engine warm, coolant temperature not below 80 °C)
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Display group 001 -Injected quantity-
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Read measured value block 1
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⇒
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◂ Indicated on display
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xxxx rpm
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xx.x mg/H
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x.xx V
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xxx.x °C
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1
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2
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3
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4
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◂ Display zones
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Specification
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Evaluation
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Coolant temperature
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80...110 °C
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---
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Modulating piston movement sender voltage
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1.45...1.90 V
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Injected quantity
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2.2...9 mg/H
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=> Page 01-90
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Engine speed
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840...903 rpm1)
800...860 rpm2)
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---
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1) Vehicles with manual gearbox
2) Vehicles with automatic gearbox
Evaluation: Injected quantity display
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|---|
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V.A.G 1551 display
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Possible fault cause
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Fault elimination
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Below 2.2 mg/H
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- Injection pump too rich
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- Renew injection pump => Page 23-19
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Above 9 mg/H
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- Engine too cold
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- Run engine at increased speed to warm up and repeat check
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- Injection pump too lean
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- Renew injection pump => Page 23-19
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Evaluation: Modulating piston movement sender voltage display
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V.A.G 1551 display
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Possible fault cause
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Fault elimination
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Below 1.45 V
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- Injection pump too rich
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- Renew injection pump => Page 23-19
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Above 1.90 V
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- Engine too cold
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- Run engine at increased speed to warm up and repeat check
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- Injection pump too lean
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- Renew injection pump => Page 23-19
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Display group 002 at idling speed (engine warm, coolant temperature not below 80 °C)
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Display group 002 -Idling speed-
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Read measured value block 2
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⇒
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◂ Indicated on display
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xxxx rpm
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xxx.x %
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xxx
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xxx.x °C
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1
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2
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3
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4
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◂ Display zones
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Specification
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Evaluation
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Coolant temperature
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80...110 °C
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---
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Operating mode
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010
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=> Page 01-92
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Accelerator pedal position
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0 %
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=> Page 01-92
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Engine speed
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840...903 rpm1)
800...860 rpm2)
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---
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1) Vehicles with manual gearbox
2) Vehicles with automatic gearbox
Evaluation: Accelerator pedal position display
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V.A.G 1551 display
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Possible fault cause
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Fault elimination
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1...100 %
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- Accelerator position sender -G79 incorrectly set or defective
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- Check G-79 and adjust if necessary
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- Wiring open circuit to G79
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Evaluation: Operating condition display
Relevance of figures in 3-digit number block for engine operating condition:
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Significance when display = 1
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x
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x
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x
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Engine operating condition
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1
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Air conditioner compressor switched on
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1
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Idling switch closed
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1
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Increased idling speed because air conditioner is switched on
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Display group 003 at idling speed (engine warm, coolant temperature not below 80 °C)
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Display group 003 -Exhaust gas recirculation-
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Read measured value block 3
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⇒
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◂ Indicated on display
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xxxx rpm
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xxx mg/H
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xxx mg/H
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xxx %
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1
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2
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3
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4
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◂ Display zones
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Specification
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Evaluation
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Duty cycle from exhaust gas recirculation valve
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4...95 %
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---
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Air mass drawn in (actual)
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230...450 mg/H
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=> Page 01-94
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Air mass drawn in (specified)
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230...450 mg/H
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=> Page 01-93
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Engine speed
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840...903 rpm1)
800...860 rpm2)
|
---
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1) Vehicles with manual gearbox
2) Vehicles with automatic gearbox
Evaluation: Air mass drawn in (specified) display
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V.A.G 1551 display
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Possible fault cause
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Fault elimination
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Above 450 mg/H
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- Engine too cold
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- Run engine at increased speed to warm up and repeat check.
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Evaluation: Air mass drawn in (actual) display
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|---|
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V.A.G 1551 display
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Possible fault cause
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Fault elimination
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Below 230 mg/H
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- Excessive exhaust gas recirculation
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- Check exhaust gas recirculation
=> Page 23-89
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- Unmetered air
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- Check intake air system for leaks.
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Above 450 mg/H
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- Engine too cold
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- Run engine at increased speed to warm up and repeat check.
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- Insufficient exhaust gas recirculation
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- Engine running at idling speed for 3 mins., give burst on throttle.
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- Air mass meter -G70 defective
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- Check exhaust gas recirculation and air mass meter function => Page 23-89
If a fault is present the measured value block indicates a constant air mass value of approx. 550 mg/H over the total speed and load range.
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Display group 004 at idling speed (engine warm, coolant temperature not below 80 °C)
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Display group 004 -Commencement of injection-
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Read measured value block 4
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⇒
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◂ Indicated on display
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xxxx rpm
|
xx.x °
B/ATDC
|
xx.x °
B/ATDC
|
xxx %
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1
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2
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3
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4
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◂ Display zones
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Specification
|
Evaluation
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Duty cycle from commencement of injection valve
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2...95 %
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---
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Commencement of injection (actual)
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3°ATDC...4°BTDC
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=> Page 01-96
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Commencement of injection (specified)
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3°ATDC...4°BTDC
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=> Page 01-96
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Engine speed
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840...903 rpm1)
800...860 rpm2)
|
---
|
1) Vehicles with manual gearbox
2) Vehicles with automatic gearbox
Evaluation: Commencement of injection (specified) display
|
V.A.G 1551 display
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Possible fault cause
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Fault elimination
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Earlier than 4°BTDC
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- Engine too cold
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- Run engine at increased speed to warm up and repeat check.
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Evaluation: Commencement of injection (actual) display
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|---|
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V.A.G 1551 display
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Possible fault cause
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Fault elimination
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Earlier than 4° BTDC
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- Engine too cold
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- Run engine at increased speed to warm up and repeat check.
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- Injection pump set too "advanced"
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- Check commencement of injection dynamically and adjust => Page 23-25
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- Commencement of injection valve -N108 defective
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- Check -N108 => Page 01-51, final control diagnosis
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Later than 3°ATDC
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- Injection pump set extremely "retarded"
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- Check commencement of injection dynamically and adjust => Page 23-25
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- Injection adjustment blocked
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- Check -N108 => Page 01-51, final control diagnosis
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- Commencement of injection valve -N108 defective
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Display group 005
The values displayed are not relevant for fault finding within the service department.
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Display group 005 -Starting conditions-
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Read measured value block 5
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⇒
|
◂ Indicated on display
|
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xxxx rpm
|
xx.x mg/H
|
xx.x °
B/ATDC
|
xxx.x °C
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1
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2
|
3
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4
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◂ Display zones
|
Specification
|
Evaluation
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Coolant temperature
|
---
|
---
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|
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Commencement of injection (actual)
|
---
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---
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Starting quantity
|
---
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---
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Engine speed
|
---
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---
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Display group 006 with ignition switched on
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Display group 006 -Switch positions-
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Read measured value block 6
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⇒
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◂ Indicated on display
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xxx km/h
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xxx
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xxxxxx
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xxx
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1
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2
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3
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4
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◂ Display zones
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Specification
|
Evaluation
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Cruise control system1)
|
---
|
---
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|
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Cruise control system
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=> Page 01-99
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Brake pedal monitor
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=> Page 01-98
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Speed
|
---
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---
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1) 0 = Vehicles with cruise control system
255 = Vehicles without cruise control system
Evaluation: Brake pedal monitor display
Relevance of figures in 3-digit number block for brake pedal monitor:
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Significance when display = 1
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x
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x
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x
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Brake pedal monitor
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1
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Brake light switch -F- closed
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1
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Brake pedal switch -F-47- open
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1
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Clutch pedal switch -F36- open
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Evaluation: Cruise control system display
Relevance of figures in 6-digit number block for cruise control system:
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|---|
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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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x
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x
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Cruise control system
|
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1
|
1
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Cruise control system switched on
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1
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1
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1
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Setting speed
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1
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1
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1
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Resuming setting speed
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1
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OFF button operated
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Display group 007 with ignition switched on (engine cold and not running)
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Display group 007 -Temperatures-
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|
Read measured value block 7
|
⇒
|
◂ Indicated on display
|
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xxx.x °C
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xxx.x °C
|
xxx.x °C
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1
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2
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3
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4
|
◂ Display zones
|
Specification
|
Evaluation
|
|
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|
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Coolant temperature
|
Approx. ambient temperature1)
|
=> Page 01-101
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|
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Intake manifold temperature
|
Approx. ambient temperature1)
|
=> Page 01-101
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No display
|
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Fuel temperature
|
Approx. ambient temperature1)
|
=> Page 01-101
|
1) Details of temperature specifications are not possible. When the engine is cold the fuel, intake air and coolant temperatures must equate approximately to ambient temperature. If a temperature deviates noticeably then the relevant sender must be checked.
Evaluation: Fuel temperature display
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
- 5.4 °C
|
- Short circuit or fuel temperature sender -G81 defective
|
- Check G81 => Page 23-56
If a fault is present the measured value block indicates a fuel temperature of -5.4 °C
|
Evaluation: Intake manifold temperature display
|
|
|---|
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
Approx. 136.8 °C
|
- Intake manifold temperature sender -G72 defective
|
- Check G72 => Page 23-51
If a fault is present the measured value block indicates a fuel temperature of approx.136.8 °C
|
Evaluation: Coolant temperature display
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
Large deviation from ambient temperature
|
- Short circuit or coolant temperature sender -G62 defective
|
- Check G62 => Page 23-40
If a fault is present the fuel temperature is shown alternatively
|
Display group 009
The values displayed are not relevant for fault finding within the service department.
|
Display group 009 -Injected quantity limitation-
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|
Read measured value block 9
|
⇒
|
◂ Indicated on display
|
|
|
|
xxxx rpm
|
xx.x mg/H
|
xx.x mg/H
|
x.xx V
|
|
|
|
1
|
2
|
3
|
4
|
◂ Display zones
|
Specification
|
Evaluation
|
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No display
|
---
|
---
|
|
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Injected quantity limitation from automatic gearbox during gear change
|
---
|
---
|
|
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|
Injected quantity (cruise control system active)
|
---
|
---
|
|
|
Engine speed
|
---
|
---
|
Display group 012
The values displayed are not relevant for fault finding within the service department.
|
Display group 012 -Glow plug system-
|
|
Read measured value block 12
|
⇒
|
◂ Indicated on display
|
|
|
|
xxxx
|
xx.xx sek.
|
xx.x V
|
xxx.x °C
|
|
|
|
1
|
2
|
3
|
4
|
◂ Display zones
|
Specification
|
Evaluation
|
|
|
|
|
|
Coolant temperature
|
---
|
---
|
|
|
|
|
Supply voltage from control unit
|
---
|
---
|
|
|
|
Pre-glow period
|
---
|
---
|
|
|
Not relevant
|
---
|
---
|
Display group 013 at idling speed (engine warm, coolant temperature not below 80 °C)
|
Display group 013 -Idling speed smooth running control-
|
|
Read measured value block 13
|
⇒
|
◂ Indicated on display
|
|
|
|
x.xx mg/H
|
x.xx mg/H
|
x.xx mg/H
|
|
|
|
|
1
|
2
|
3
|
4
|
◂ Display zones
|
Specification
|
Evaluation
|
|
|
|
|
|
No display
|
|
---
|
|
|
|
|
Different quantity injected Cyl. 1 and Cyl. 3
|
- 2.0...+ 2.0 mg/H
|
=> Page 01-105
|
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|
|
Different quantity injected Cyl. 2 and Cyl. 3
|
- 2.0...+ 2.0 mg/H
|
=> Page 01-105
|
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|
Different quantity injected Cyl. 4 and Cyl. 3
|
- 2.0...+ 2.0 mg/H
|
=> Page 01-105
|
Evaluation: Idling speed smooth running control display
The injection system is equipped with an idling speed smooth running control. There may be power differences between the individual cylinders (component tolerances, injector delivery, compressions etc.) which are recognised and equalized via selective injected quantities.
Recognition at idling speed is via the signal from the engine speed sender which delivers four signals per crankshaft revolution to the control unit. If the signals are delivered at the same rhythm then all cylinders work the same. If one cylinder is weaker then the crankshaft takes longer for the next half revolution. Conversely a more powerful cylinder accelerates the crankshaft so less time is taken.
If the control unit recognises a difference, then the relevant cylinder is given more or less fuel, until the engine runs evenly again.
The measured value block displays the injected quantity differences of the individual cylinders compared with No. 3 cylinder that is required to ensure an even engine idling speed.
+... mg/H: The relevant cylinder is less powerful than No. 3 cylinder and is therefore supplied with more fuel.
-... mg/H: The relevant cylinder is more powerful than No. 3 cylinder and is therefore supplied with less fuel.
Display group 015
The values displayed are not relevant for fault finding within the service department.
|
Display group 015 -Fuel consumption-
|
|
Read measured value block 15
|
⇒
|
◂ Indicated on display
|
|
|
|
xxxx rpm
|
xx.x mg/H
|
xx.xx l/h
|
xx.x mg/H
|
|
|
|
1
|
2
|
3
|
4
|
◂ Display zones
|
Specification
|
Evaluation
|
|
|
|
|
|
Injected quantity requirement (driver's requirement via accelerator pedal)
|
---
|
---
|
|
|
|
|
Fuel consumption
|
---
|
---
|
|
|
|
Injected quantity (actual)
|
---
|
---
|
|
|
Engine speed
|
---
|
---
|
Display group 000 at full throttle (test drive in 3rd gear, coolant temperature not below 80 °C)
Notes:
-
◆ When testing, accelerate vehicle at full throttle, but do not operate kickdown on automatic gearboxes.
-
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.
|
|
|---|
|
Display group 000 (decimal displayed value)
|
|
▪ Engine speed 2900...3100 rpm
|
|
Read measured value block 0
|
◂ Indicated on display
|
|
|
|
x
|
x
|
x
|
x
|
x
|
x
|
x
|
x
|
x
|
x
|
|
|
|
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
9
|
10
|
◂ Display zones
|
Specification
|
Corresponds to
|
|
|
|
|
|
|
|
|
|
|
|
Air mass
|
240...255
|
800...850 mg/H
|
|
|
|
|
|
|
|
|
|
|
Fuel temperature
|
91...201
|
20...80°C
|
|
|
|
|
|
|
|
|
|
Intake manifold temperature
|
182...50
|
10...100°C
|
|
|
|
|
|
|
|
|
Coolant temperature
|
80...35
|
80...110°C
|
|
|
|
|
|
|
|
Atmospheric pressure
|
Not relevant
|
---
|
|
|
|
|
|
|
Intake manifold pressure
|
168...219
|
1747...2250 mbar
|
|
|
|
|
|
Injected quantity
|
190...215
|
38...43 mg/stroke
|
|
|
|
|
Accelerator pedal position
|
255
|
100 %
|
|
|
|
Commencement of injection
|
112...213
|
6...14°BTDC
|
|
|
Engine speed
|
138...148
|
2900..3100 rpm
|
Display group 004 at full throttle (test drive in 3rd gear/3rd driving range, coolant temperature not below 80 °C)
Notes:
-
◆ When testing, accelerate vehicle at full throttle, but do not operate kickdown on automatic gearboxes.
-
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.
|
Display group 004 -Commencement of injection-
|
|
Read measured value block 4
|
⇒
|
◂ Indicated on display
|
|
|
|
xxxx rpm
|
xx.x °
B/ATDC
|
xx.x °
B/ATDC
|
xxx %
|
|
|
|
1
|
2
|
3
|
4
|
◂ Display zones
|
Specification
|
Evaluation
|
|
|
|
|
|
Duty cycle from commencement of injection valve
|
60...95 %
|
=> Page 01-109
|
|
|
|
|
Commencement of injection (actual)
|
Approx. commencement of inj. (specified)
|
=> Page 01-109
|
|
|
|
Commencement of injection (specified)
|
6...14°BTDC
|
---
|
|
|
Engine speed
|
2900...3100 rpm
|
---
|
Evaluation: Commencement of injection (actual) display
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
For large deviation from specified value (approx. 5°)
|
- Commencement of injection valve -N108 defective
|
- Check -N108 => Page 01-51, final control diagnosis
|
|
|
- Injection pump timing way off
|
- Check commencement of injection dynamically and adjust => Page 23-25
|
|
|
- Air in fuel system
|
- Check fuel supply system
|
Evaluation: Duty cycle from commencement of injection valve display
|
|
|---|
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V.A.G 1551 display
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Possible fault cause
|
Fault elimination
|
|
Below 60 or
above 95 %
|
- Commencement of injection valve -N108 defective
|
- Check -N108 => Page 01-51, final control diagnosis
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|
|
|
- Check commencement of injection dynamically and adjust => Page 23-25
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|
|
|
- Check fuel supply system
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Display group 008 at full throttle (test drive in 3rd gear/3rd driving range, coolant temperature not below 80 °C)
Notes:
-
◆ When testing, accelerate vehicle at full throttle, but do not operate kickdown on automatic gearboxes.
-
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.
|
Display group 008 -Injected quantity limitation-
|
|
Read measured value block 8
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⇒
|
◂ Indicated on display
|
|
|
|
xxxx rpm
|
xx.x mg/H
|
xx.x mg/H
|
xx.x mg/H
|
|
|
|
1
|
2
|
3
|
4
|
◂ Display zones
|
Specification
|
Evaluation
|
|
|
|
|
|
Injected quantity limitation due to mass of air drawn in (smoke prevention)
|
Above 39 mg/H
|
=> Page 01-111
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|
|
|
|
Injected quantity limitation via revs. (torque limitation)
|
39...42 mg/H
|
=> Page 01-111
|
|
|
|
Injected quantity (driver's requirement)
|
Above 39 mg/H
|
=> Page 01-111
|
|
|
Engine speed
|
2900...3100 rpm
|
---
|
Evaluation: Injected quantity (driver's requirement) display
|
|
|---|
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
Below 39 mg/H
|
- No full throttle
|
- Repeat check at full throttle
|
|
|
- Accelerator pedal position sender -G79 incorrectly adjusted or defective
|
- Check G-79 and if necessary adjust
|
Evaluation: Injected quantity limitation via revs. (torque limitation) display
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
Below 39 mg/H
|
- Speed too high or too low
|
- Read off specified value at 3000 rpm.
|
Evaluation: Injected quantity limitation due to air mass drawn in (smoke prevention) display
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
Below 39 mg/H
|
- Air mass drawn in insufficient
|
- Check exhaust gas recirculation and air mass meter function => Page 23-89
|
|
|
- Excessive exhaust gas recirculation
|
- Check exhaust gas recirculation and air mass meter function
|
Display group 010 at full throttle (test drive in 3rd gear/3rd driving range, coolant temperature not below 80 °C)
Notes:
-
◆ When testing, accelerate vehicle at full throttle, but do not operate kickdown on automatic gearboxes.
-
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.
|
Display group 010 -Air quantities-
|
|
Read measured value block 10
|
⇒
|
◂ Indicated on display
|
|
|
|
xxx mg/H
|
xxxx mbr
|
xxxx mbr
|
xxx.x %
|
|
|
|
1
|
2
|
3
|
4
|
◂ Display zones
|
Specification
|
Evaluation
|
|
|
|
|
|
Accelerator pedal position
|
100 %
|
=> Page 01-114
|
|
|
|
|
Intake manifold pressure (charge pressure)
|
1747...2250 mbar
|
=> Page 01-113
|
|
|
|
Atmospheric pressure (ambient pressure)
|
No specification
|
---
|
|
|
Air mass drawn in
|
800...1150 mg/H
|
=> Page 01-113
|
Evaluation: Air mass drawn in display
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
Below 800 mg/H
|
- Speed too low or too high
|
- Read off specified value at 3000 rpm.
|
|
|
- Charge pressure too low
|
- Check charge pressure control
=> Page 23-79
|
|
|
- Air mass meter defective
|
- Check exhaust gas recirculation and air mass meter function => Page 23-89
If a fault is present the measured value block indicates a constant air mass value of approx. 550 mg/H over the total speed and load range
|
Evaluation: Intake manifold pressure (charge pressure) display
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
Below 1747 mbar
|
- Charge pressure control defective
|
- Check charge pressure control
=> Page 23-79
|
|
Above 2250 mbar
|
- Turbocharger defective
|
|
Evaluation: Accelerator pedal position display
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
Below 100 %
|
- No full throttle
|
- Repeat check at full throttle.
|
|
|
- Accelerator pedal position sender -G79 incorrectly adjusted or defective
|
- Check G-79 and if necessary adjust
|
Display group 011 at full throttle (test drive in 3rd gear/3rd driving range, coolant temperature not below 80 °C)
Notes:
-
◆ When testing, accelerate vehicle at full throttle, but do not operate kickdown on automatic gearboxes.
-
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.
|
Display group 011 -Charge pressure control-
|
|
Read measured value block 11
|
⇒
|
◂ Indicated on display
|
|
|
|
xxxx rpm
|
xxxx mbr
|
xxxx mbr
|
xxx %
|
|
|
|
1
|
2
|
3
|
4
|
◂ Display zones
|
Specification
|
Evaluation
|
|
|
|
|
|
Duty cycle from charge pressure limitation valve
|
45...95 %
|
---
|
|
|
|
|
Charge pressure (actual)
|
1747...2250 rpm
|
=> Page 01-116
|
|
|
|
Charge pressure (specified)
|
1747...2250 mbar
|
---
|
|
|
Engine speed
|
2900...3100 rpm
|
---
|
Evaluation: Charge pressure (actual) display
|
|
|---|
|
V.A.G 1551 display
|
Possible fault cause
|
Fault elimination
|
|
Below 1747 mbar
|
- Charge pressure control defective
|
- Check charge pressure control
|
|
|
- Turbocharger defective
|
|
|
|
- Charge pressure hose not connected to control unit
|
- Connect charge pressure hose
|
|
Above 2250 mbar
|
- Turbocharger defective
|
- Check charge pressure control
|
| 
