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Evaluating measured value blocks, display groups 30...49, 99 -Lambda regulation-
Evaluating measured value blocks, display groups 30...49, 99 -Lambda regulation-
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Display group 30 -Lambda regulation-
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▪ Engine running at idling speed
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Read measured value block 30
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◂ Indicated on display
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xxx
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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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Lambda regulation status after catalyst
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110
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Lambda regulation status before catalyst
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111
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=> Page 01-120
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Notes on display zones 1 and 2:
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◆ The Lambda probe heating may be switched on or off depending on the operating condition of the engine, i.e. the 1st position in display zones 1 or 2 may show 1 or 0.
Significance of figures in 3-digit number block, display zones 1 and 2 - status of Lambda regulation before and after catalyst
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Significance if display = 1
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1
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2
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3
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1
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Lambda regulation active
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1
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Lambda probe operationally ready
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1
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Lambda probe heating on
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Display group 32 -Lambda regulation- Lambda learnt values
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▪ Engine running at idling speed
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Read measured value block 32
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◂ Indicated on display
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xx.x %
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xx.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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◂ Display zones
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Specification
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Evaluation
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Lambda learnt value at part load (range 2)
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-10...10 %
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=> Page 01-122
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Lambda learnt value at idling speed (range 1)
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-10...10 %
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=> Page 01-122
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Notes on display zones 1 and 2:
Low values indicate that the engine is running too rich and therefore the Lambda regulation is leaning the mixture.
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◆ High values indicate that the engine is running too lean and therefore the Lambda regulation enriches the mixture.
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◆ If there is no voltage supply to the control unit and the fault memory is erased, all the values learnt will be cancelled.
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◆ Range 1 - The effects of the fault (e.g. unmetered air) decrease as the engine speed increases. The injection period is modified by a fixed amount by this learnt value. This amount is not dependent upon the basic injection period.
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◆ Range 2 - The effects of the fault (e.g. faulty injector) increase as the engine speed increases. This learnt value effects the injection period proportionally. This change is dependent on the basic injection period.
Initiating learning process: Control unit in mode 04, Basic settings
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◆ Learning conditions for idling: Idling, coolant temperature min. 75 °C, intake air temperature max. 90 °C
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◆ Learning conditions for part load: coolant temperature min. 75 °C, intake air temperature max. 90 °C
Evaluating display zone 32, display zones 1 and 2 - Lambda learnt values
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Appears on display
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Possible fault cause
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Fault elimination
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Low Lambda learnt values
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- Low learnt values at idling but with normal learnt values at part throttle: possible oil dilution (high level of fuel in oil)
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- Disappears after motorway drive or oil change
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- Injector leaking
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- Check injector
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- Fuel pressure too high
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- Check fuel pressure regulator and holding pressure => Page 24-74
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- Activated charcoal filter solenoid valve 1 permanently open
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- Check activated charcoal filter solenoid valve 1 => Page 01-81, Final control diagnosis
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- Air mass meter defective
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- Check air mass meter => Page 24-34
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- Lambda probe heating defective or Lambda probe soiled
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- Check Lambda probe heating
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Appears on display
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Possible fault cause
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Fault elimination
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High Lambda learnt values
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- High learnt values at idling speed, not so high learnt values at part throttle: possible unmetered air in area of intake manifold
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- Check intake air system for leaks
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- Unmetered air between air mass meter and throttle valve
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- Rectify cause
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- Injector blocked
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- Check quantity injected rate
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- Display zones 1 and 2 high: Air mass meter defective
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- Check air mass meter => Page 24-34
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- Fuel pressure too low
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- Check fuel pressure regulator and holding pressure => Page 24-74
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- Unmetered air at exhaust manifold gasket
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- Lambda probe heating defective or Lambda probe soiled
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- Check Lambda probe heating
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Display group 33 -Lambda regulation- Lambda regulation values
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▪ Engine running at idling speed
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Read measured value block 33
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◂ Indicated on display
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xx.x %
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x.xxx V
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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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Lambda probe voltage, Lambda probe before catalyst
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1.4...1.6 V
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---
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Lambda regulator before catalyst
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-10.0...10.0 %
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=> Page 01-125
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Notes on display zone 1:
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◆ The display must fluctuate around 0. If constant 0 is displayed, the Lambda regulation has switched from regulation to control, because there is a fault in the Lambda regulation. Interrogate fault memory => Page 01-17.
Notes on display zone 2:
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◆ The voltage signal "rich mixture (low level of residual oxygen)" is below 1.5 V.
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◆ The voltage signal "lean mixture (high level of residual oxygen)" is above 1.5 V.
Evaluating display group 33, display zone 1 - Lambda regulator before catalyst
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Appears on display
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Possible fault cause
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Fault elimination
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Outside tolerance range
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- Minus range: Mixture too rich, Lambda control weakens mixture
- Positive range: Mixture too lean, Lambda control enriches mixture
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- Wait 30 seconds until the display has stabilised
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- Unmetered air
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- Check intake system for leaks
=> Page 24-79
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- Injector defective
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- Check injection rate => Page 24-65
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- Lambda learnt value on limit
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- Check Lambda learnt value in display group 32
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Display group 34 -Lambda regulation- Lambda probe diagnosis before catalyst (ageing check)
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▪ Vehicle stationary, engine running at increased idling speed
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▪ Control unit in mode 04-Basic settings
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Read measured value block 34
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◂ Indicated on display
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xxxx rpm
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xxx.x °C
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xx.xx
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Text
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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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Result of Lambda probe before catalyst age check (test OFF/test ON/B1-P1 OK / B1-P1 n.OK)
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B1-P1 OK
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---
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Dynamic factor Lambda probe before catalyst
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---
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Catalyst temperature
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min. 350 °C
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---
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Engine speed
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1 800...2 200 rpm
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Note on display zone 2:
Value calculated from engine speed and engine load.
Note on display zone 4:
The control unit compares the adjustment frequency of the Lambda probes evaluation circuitry with a specification stored in the control unit. If this value is not reached, the message: "B1-P1 n.OK" is indicated in display zone 4.
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Display group 36 -Lambda regulation- Operational readiness of probe after catalyst
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▪ Vehicle stationary, engine running at high idling speed at 1 800...2 800 rpm
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▪ Control unit in mode 04-Basic settings
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Read measured value block 36
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◂ Indicated on display
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x.xxx V
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Text
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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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Lambda probe after catalyst test (Test OFF/Test ON/B1-P2 OK/ B1-P2 n.OK)
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B1-P2 OK
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Lambda probe voltage, Lambda probe after catalyst
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0.100...0.900 V
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=> Page 01-128
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Note:
It can take a few minutes until display jumps from "Test ON" to "B1-P2 OK".
Evaluating display group 36, display zone 3 - Lambda probe voltage, Lambda probe after catalyst
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Appears on display
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Possible fault cause
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Fault elimination
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Constant 1.100 V
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- Short to positive via:
- Lambda probe, probe wiring, earth wiring, engine control unit
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- Check Lambda probe wiring
=> Page 24-97
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Constant between
0.400...0.500 V
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- Open circuit via:
- Lambda probe, probe wiring, earth wiring, engine control unit
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Constant 0.000 V
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- Short to earth via:
- Lambda probe, probe wiring, earth wiring, engine control unit
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Display group 41 -Lambda regulation- Lambda probe heating
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▪ Engine running at idling speed
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Read measured value block 41
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⇒
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◂ Indicated on display
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Text
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Text
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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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Lambda probe heating after catalyst
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Htg.aC.ON
Htg.aC.OFF
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Lambda probe heating before catalyst
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Htg.bC.ON
Htg.bC.OFF
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Note:
The Lambda probe heating may be switched ON or OFF depending on the operating conditions of the engine, therefore the display in display zone 2 or 4 may show "Htg.b(a)C.ON" or alternating from "Htg.b(a)C.ON" to Htg.b(a)C.OFF".
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Display group 99 -Lambda regulation- Lambda regulation operating condition
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▪ Engine running at idling speed
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▪ Control unit in mode 04-Basic setting, Lambda regulation off
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▪ Control unit in mode 08-Read measured value block, Lambda regulation on
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Read measured value block 99
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⇒
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◂ Indicated on display
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xxxx rpm
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xx.x °C
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x.x %
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Text
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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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Lambda regulation operating mode
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λ-Reg. OFF or
λ-Reg. ON
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Lambda regulator before catalyst
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-10.0...10.0 %
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=> Page 01-125
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Coolant temperature
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80...110 °C
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=> Page 01-108
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Engine speed (idling speed)
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750...860 rpm
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=> Page 01-102
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Notes on display zone 4:
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◆ For a defined fault finding the Lambda regulation is switched off when selecting display group 99 under "Basic setting" or switched on under "Read measured value block".
When the function 04 "Basic setting" is exited the Lambda regulation is automatically active again.
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◆ It is possible to switch between the function 04 "Basic setting" and the function 08 "Read measured value block" by pressing the keys 4 and 8 on V.A.G 1551/1552.
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