SEAT Workshop Service and Repair Manuals

Evaluating measured value blocks, display groups 30...49,99 -Lambda regulation-

Display group 30 -Lambda regulation-
l  Engine running at idling speed
Read measured value block 30			→	← Indicated on display
xxx	xx.x	------	------
1	2	3	4	← Display fields	Specification	Evaluation
		Operating status of Lambda regulation after catalytic converter			110	→ Anchor
	Operating status of Lambda regulation before catalytic converter				111	→ Anchor

Note on display field 2: t  The 3rd display position is not set to 1 until in part throttle range.

Significance of 3 digit number block, display fields 1 and 2:

Significance if display = 1
1	2	3	Significance
		1	Lambda regulation active
	1		Lambda probe operationally ready
1			Lambda probe heating on

Display group 32 -Lambda regulation - Lambda learnt values-
l  Engine running at idling speed
Read measured value block 32			→	← Indicated on display
xx.x %	xx.x %	------	------
1	2	3	4	← Display fields	Specification	Evaluation
		Lambda before catalytic converter learnt value at part load (multiplicative)			-10.0...10.0%	→
	Lambda before catalytic converter learnt value at idle (additive)				-10.0...10.0%	→

Notes on display fields 1 and 2: t  Low values: the engine is running too rich and therefore the Lambda regulation is leaning the mixture. t  High values: the engine is running too lean and therefore the Lambda regulation is enriching the mixture. t  When there is no voltage supply to the control unit, all learnt values are restarted. t  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. t  mul.= multiplicative - The effects of the fault (e.g. faulty injector) will reduce 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. t  Learnt value conditions, partial throttle: coolant temperature 75 °C min.; intake air temperature, 90 °C max., car running.

Display group 32, Lambda regulation - Lambda learnt values

Reading -V.A.G 1551-	Possible fault cause	Fault elimination
Low Lambda learnt values	t  Low learnt values at idling, with normal learnt values at part throttle: possible oil dilution (high level of fuel in oil)	–  Disappears after motorway drive or oil change
	t  Injector leaking	–  Check injectors → Chapter
	t  Fuel pressure too high	–  Check fuel pressure regulator and holding pressure → Chapter
	t  Activated charcoal filter solenoid valve 1 permanently open	–  Check activated charcoal filter solenoid valve 1 → Chapter; Final control diagnosis
	t  Lambda probe heating defective or Lambda probe soiled	–  Check the Lambda probe heating before catalytic converter → Chapter

Reading -V.A.G 1551-	Possible fault cause	Fault elimination
High Lambda learnt values	t  Learnt values at idling speed, not so high learnt values at part throttle: possible unmetered air in area of intake manifold	–  Check intake system for leaks (unmetered air) → Chapter
	t  Unmetered air between air cleaner and throttle valve t  Injector blocked	–  Rectify cause –  Check injection rate → Chapter
	t  Fuel pressure too low	–  Check fuel pressure regulator and holding pressure → Chapter
	t  Unmetered air at exhaust manifold gasket
	t  Lambda probe heating defective or Lambda probe soiled	–  Check the Lambda probe heating before catalytic converter → Chapter

Display group 33 -Lambda regulation - Lambda regulation values-
l  Engine running at idling speed
Read measured value block 33			→	← Indicated on display
xx.x %	x.xxx V	------	------
1	2	3	4	← Display fields	Specification	Evaluation
		Lambda probe voltage, Lambda probe before catalytic converter			0.3...0.6 V	---
	Lambda regulator before catalytic converter				-15.0...15.0%	→

Notes on display field 1: t  The displayed value 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 → Chapter. Notes on display field 2: t  The voltage signal “rich mixture (low level of residual oxygen)” is approx. 0.7...1.0 V t  The voltage signal “lean mixture (low level of residual oxygen)” is approx. 0.0...0.3 V t  When changing from “rich” to “lean” and back again (λ = 1.0) the voltage jump will change from 0.7...1.0 V to 0.0...0.3 V or back again. t  Due to the steep voltage jumps the Lambda control cannot keep the ideal mixture composition λ = 1.0 constant. The control fluctuates constantly between conditions “slightly too lean” and “slightly too rich”.

Lambda probe voltage Uλ in mV t  A: High Lambda probe voltage t  Rich mixture (excess of fuel or shortage of air) t  Higher CO value t  B: Low Lambda probe voltage t  Lean mixture (shortage of fuel or excess air) t  Lower CO value

Evaluating display group 33, display field 1 -Lambda regulator before catalytic converter-

Appears on display	Possible fault cause	Fault elimination
Outside tolerance range	t  Minus range: Mixture too rich, Lambda control weakens mixture t  Positive range: Mixture too lean, Lambda control enriches mixture	–  Wait 30 seconds until the display has stabilised
	t  Unmetered air	–  Check intake system for leaks (unmetered air) → Chapter
	t  Injector defective	–  Check injectors → Chapter
	t  Lambda learnt values on limit	–  Check Lambda learnt values in display group 32

Display group 34 -Lambda regulation - Lambda probe diagnosis before catalytic converter (ageing check via amplitude quality monitoring)-
–  Give two throttle bursts, raising RPMs over 5000.
l  Vehicle stationary, engine running at increased idling speed l  Control unit in mode 04- basic setting
Read measured value block 34			→	← Indicated on display
xxxx RPM	xxx.x °C	x.xx s	Text
1	2	3	4	← Display fields	Specification	Evaluation
				Result of ageing check of Lambda probe before catalytic converter (Test OFF / Test ON / B1-P1 OK / B1-P1 not OK)	B1–P1 OK	---
			Lambda probe period before catalytic converter		Max. 1.0 s	---
		Catalytic converter temperature			----	---
	Engine speed				1500..3900 RPM	---

Note on display field 3 and 4: t  The period calculated is the time between two jumps in voltage (eg: rich - lean - rich) of the Lambda probe and thus indicates the ageing status of the probe. If the period exceeds the predetermined time, display field 4 will read = B1-P1 not OK.

Display group 36 -Lambda regulation - Lambda probe regulation after catalytic converter-
l  Vehicle stationary, brake depressed, engine running at high idle (1500...4000 RPM)
l  Control unit in mode 04 - basic setting -
Read measured value block 36			→	← Indicated on display
x.xxx V	Text	-----	-----
1	2	3	4	← Display fields	Specification	Evaluation
						---
		Check Lambda probe after catalytic converter (Test OFF/Test ON/B1-P2 OK / B1-P2 not OK)			B1-P2 OK”	---
	Lambda probe voltage, Lambda probe after catalytic converter				0.000...1.000 V	→

Evaluating display group 36, display field 1 -Lambda probe voltage after catalytic converter-

Reading -V.A.G 1551-	Possible fault cause	Fault elimination
Constant 1.100 V	t  Short to positive via: Lambda probe, probe wiring, earth wiring, engine control unit	–  Checking Lambda probe wiring, Lambda probe 2 →  –  Check Lambda probe 2 basic voltage →
Constant between 0,400...0,500 V	t  Open circuit in: Lambda probe, probe wiring, earth wiring, engine control unit
Constant 0.000 V	t  Short to earth via: Lambda probe, probe wire, earth wire, engine control unit

Display group 37 -Lambda regulation - Lambda probes-
l  Whilst driving
Read measured value block 37			→	← Indicated on display
xxx %	x.xxx V	xxx.xxx	Text
1	2	3	4	← Display fields	Specification	Evaluation
				Checking lambda probes (Test OFF/ Test ON/Syst. OK/Syst. not OK)	Syst.OK
			Not relevant for Service department		---	---
		Lambda probe voltage, Lambda probe before catalytic converter			0.000.....1.000 V	→
	Engine load				12.0...100%	---

Display group 41 -Lambda regulation - Lambda probe heating-
l  Engine running at idling speed
Read measured value block 41			→	← Indicated on display
-----	Text	xx Ohm	Text
1	2	3	4	← Display fields	Specification	Evaluation
				Lambda probe heating after catalytic converter	Htg.aC.ON Htg.aC.OFF	---
			Not relevant for Service department		-----	-----
		Lambda probe heating before catalytic converter			Htg.bC.ON Htg.bC.OFF	-----

Note! Depending on engine load, Lambda probe heating is switched on or off, so display fields 2 and 4 may read Htg. b(a)Ca ON or, alternately Htg. b(a)C ON / Htg. b(a)C OFF.

Display group 46 -Lambda regulation - catalytic converter diagnosis (conversion test)-
l  Control unit in mode 04 -basic setting- l  Vehicle stationary, engine running at increased idling speed
Read measured value block 46			→	← Indicated on display
xxxx RPM	xxxx °C	xx %	Text
1	2	3	4	← Display fields	Specification	Evaluation
				Result of catalytic converter conversion test (Test OFF/Test ON/Cat B1 OK/Cat B1 n.OK)	CatB1 OK	---
			Measurement value of catalytic converter conversion		50% minimum	---
		Catalytic converter temperature			300°C minimum	---
	Engine speed				1500...3900 RPM	---

Note on display group 46: t  Requirements for catalytic conversion test: No faults stored in memory, engine idling, coolant temperature 60...120 5C, Lambda regulation active and stable.

Display group 99 -Lambda regulation - Lambda regulation operating status-
l  Engine running at idling speed
Read measured value block 99			→	← Indicated on display
xxxx RPM	xxx.x oC	x.x %	Text
1	2	3	4	← Display fields	Specification	Evaluation
				Operating status of Lambda regulation before catalytic converter	Reg. λ OFF o Reg. λ ON	---
			Lambda regulator before catalytic converter		-10.0...10.0%	→
		Coolant temperature			80...110 °C	→
	Engine speed (idling speed)				700...900 min	→