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Evaluating measured value blocks, display grps 30...49, 99 -Lambda regulation-
Evaluating measured value blocks, display grps 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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---
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---
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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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Status of Lambda regulation after catalyst1)
▪ Catalyst temperature at least 400.0 °C
▪ (=>display group 34, display zone 2)
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111
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Status of Lambda regulation before catalyst
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111
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=> Page 01-79
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Notes on display zones 1 and 2:
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◆ The first position in 3-digit number block fluctuates between 0 and 1 (Lambda probe heating off and on).
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◆ Depending on status of Lambda regulation 0 or 1 is displayed alternately in 3-digit number block.
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◆ The bits in display zones 1 and 2 are set to 1, when the catalyst temperature has exceeded 400.0 °C (=> display group 34, display zone 2).
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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Significance
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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 before catalyst
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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 (multiplicative) before catalyst
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-10.0...10.0 %
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=> Page 01-82
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Lambda learnt value at idling speed (additive) before catalyst
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-10.0...10.0 %
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=> Page 01-82
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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 all the values learnt will be cancelled.
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◆ add = additive - The effects of the fault (e.g. unmetered air) will reduce as the engine speed increases. The injection period will be modified by a fixed amount for additive learnt values. This amount is not dependent upon the basic injection period.
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◆ mul = multiplicative - The effects of the fault (e.g. faulty injector) will increase as the engine speed increases. A multiplicative learnt value is a proportional change to the injection period. 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 group 32, display zones 1 and 2 - Lambda learnt values 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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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 24-77
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- Tank venting valve for activated charcoal filter permanently open
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- Check tank venting valve
=> Page 01-46, final control diagnosis
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- Lambda probe heating defective or Lambda probe soiled
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- Check Lambda probe heating 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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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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- Injector blocked
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- Check injectors
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- Fuel pressure too low
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- Check fuel pressure regulator and holding pressure => Page 24-77
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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 before catalyst
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Display group 33 -Lambda regulation- Lambda regulation values before catalyst
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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 before catalyst
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1.000...2.000 V
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Lambda regulator before catalyst
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-10.0...10.0 %
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=> Page 01-85
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Notes on display zone 1:
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◆ The display must fluctuate around 0.0 %. If constant 0.0 % is displayed, the Lambda regulation has switched from regulation to control, because there is a fault in the Lambda regulation. Interrogate fault memory => Page 01-16.
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 24-86
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- Injector defective
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- Check injectors
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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 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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◂ 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 catalyst1)
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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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◂ Indicated on display
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xxxx rpm
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xxx.x °C
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xx.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 01-85
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Coolant temperature
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80.0...110.0 °C
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=> Page 01-65
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Engine speed (idling speed)
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600...800 rpm
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=> Page 01-58
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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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