SEAT Workshop Service and Repair Manuals

Analysis measured value block, display groups 30...49 -lambda control-

Display group 30 -lambda control-
l  Engine idling
Read measured value block 30			→	◂ Message on the display
xxx	xx.x %	---	---
1	2	3	4	◂ Display fields	Target value	Analysis
		Post-catalyst lambda control operative state			110	→ Chapter
	Pre-catalyst lambda control operative state				111	→ Chapter

t	Notes on display field 2:

t	At half load the third digit changes to 1.

Meaning of the 3-digit numerical block, display fields 1:

Meaning in case of digits
1	2	3	Meaning
		1	Lambda control active
	1		Lambda probe ready
1			Lambda probe heating ON

Display group 32 - lambda control - lambda learning values
l  Engine idling
Read measured value block 32			→	◂ Message on the display
xx.x %	xx.x %
1	2	3	4	◂ Display fields	Target value	Analysis
		Pre-catalyst lambda self-adaptive value at half load (multiplicative)			-10...10 %	→ Anchor
	Pre-catalyst lambda self-adaptive value at idling revs (additive)				-10...10 %	→ Anchor

t	Notes on the display fields 1 and 2:

t	Low values: the engine runs on an overly rich mixture, thus the lambda control makes the mixture leaner.

t	High values: the engine runs on an overly lean mixture, thus the lambda control enriches the mixture.

t	When the control unit receives no voltage, all the self-adaptive values are restarted.

t	add = additive - the fault (e.g., infiltrated air) loses influence as revs are raised. In the case of the self-adaptive additive value, the injection timing changes according to a fixed magnitude that does not depend on basic ignition timing.

t	mul = multiplicative - the fault (e.g. faulty injector) loses influence as revs are raised. In the case of the self-adaptive multiplicative value there is a percentile change in the injection timing that depends on basic ignition timing.

Analysis display group 32, display fields 1 and 2 - lambda self-adaptive values

Display -V.A.G. 1551-	Possible cause of the fault	Elimination of the fault
Low lambda learning values	t  Low learning values at idling, with normal self-adaptive values at half load: possibility of diluted oil (high fuel content in the oil)	–  Disappears when driving on the motorway or after changing the oil
	t  Injector leaky	–  Test the injectors → Chapter
	t  Fuel pressure very high	–  Test the Fuel pressure regulator and the retaining pressure → Chapter
	t  Solenoid valve 1 for activated charcoal filter always open	–  Solneoid valve 1 for activated charcoal filter → Chapter, Final control diagnosis
	t  Fault in the lambda probe heating or lambda probe is dirty	–  Test the pre-catalyst lambda probe heating → Chapter

Display -V.A.G. 1551-	Possible cause of the fault	Elimination of the fault
High lambda self-adaptive values	t  High learning values at idling, with lower self-adaptive value at half load: possibility of infiltrated air in the upper part of the intake manifold	–  Test the intake system for leakage → Anchor
	t  Injector blocked	–  Test the injectors → Chapter
	t  Fuel pressure very low	–  Test the fuel pressure regulator and the retaining pressure → Chapter
	t  Infiltrated air in the exhaust manifold gasket
	t  Fault in the lambda probe heating or lambda probe is dirty	–  Test the pre-catalyst lambda probe heating → Chapter

Display group 33 -lambda regulation- lambda regulation values
l  Engine idling
Read measur. value block 33			→	◂ The display reads
xx.x %	x.xxx V	--	--
1	2	3	4	◂ Display fields	Target value	Analysis
		Pre-catalyst lambda probe voltage			0.3...0.6 V	--
	Pre-catalyst lambda regulator				-15.0...15.0 %	--

t	Note on display field 1:

t	The value displayed should oscillate around 0.0 %. If a constant 0.0% is displayed, lambda regulation has switched from the regulation to the control mode due to a fault in lambda regulation. Consult the fault memory → Chapter.

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

Analysis display group 33, display field 1 - pre-catalyst lambda probe

Display -V.A.G. 1551-	Possible cause of the fault	Elimination of the fault
Outside the target range	t  Negative range: engine very rich, the lambda control reduces the richness of the mixture t  Positive range: engine very lean, the lambda control enriches the mixture	–  Wait 30 seconds for the value displayed to stabilise
	t  Infiltrated air	–  Test the intake system for leakage → Anchor
	t  Injector faulty	–  Test the injectors → Chapter
	t  Self-adaptive lambda values, to limit	–  Test self-adaptive lambda values in the display group 32

Display group 34 - lambda regulation - diagnosis pre-catalyst lambda probe (ageing test via amplitude quality monitoring)
–  Give two throttle bursts, raising revs to over 5000/min. l  Vehicle stopped, engine running at fast idle l  Control unit is mode 04 - basic settings
Read measur. value block 34			→	◂ The display reads
xxxx/min	xxx.x °C	xx.xx s	text
1	2	3	4	◂ Display fields	Target value	Analysis
				Result of pre-catalyst lambda probe ageing test (Test OFF/Test ON/F1-S1 OK/F1-S1 not OK)	F1-S1 OK	--
			Pre-catalyst lambda probe period		max. 1.0 s	--
		Catalyst temperature			300 °C. approx.	--
	Engine revs				1500...3900/min	--

t	Note on display fields 3 and 4:

t	The period is the time between two voltage jumps (for example, rich - lean - rich) of the lambda probe and thus indicates the probe ageing state. If the period exceeds the predetermined time, display field 4 shows = F1-S1 not OK.

Display group 36 -lambda control- control after the catalyst
l  Engine idling
Read measured value block 36			→	◂ Message on the display
xx.x V	text	---	---
1	2	3	4	◂ Display fields	Target value	Analysis
	Post-catalyst lambda probe voltage				0.000...1.000 V	→ Anchor

Analysis display group 36, display field 1 - post-catalyst lambda probe

Display -V.A.G. 1551-	Possible cause of the fault	Elimination of the fault
constant 1.100 V	t  Short circuit to positive caused by lambda probe, probe wire, earth wire, engine control unit	–  Test lambda probe wiring → Chapter
constant between 0.400 V...0.500 V	t  Open circuit caused by lambda probe, probe wire, earth wire, engine control unit
constant 0.000 V	t  Short circuit to earth caused by lambda probe, probe wire, earth wire, engine control unit

Display group 41 -lambda control- lambda probe heating
l  Engine idling
Read measured value block 41			→	◂ Message on the display
--	text	xx Ohm	text
1	2	3	4	◂ Display fields	Target value	Analysis
				Post-catalyst lambda probe heating	CfS dCa ON CfS dCa OFF	---
			Without value for technical assistance		---	---
		Pre-catalyst lambda probe heating			CfS aCa ON CfS aCa OFF	---

According to the engine load state, the lambda probe heaters are activated and desactivated; that is in the display fields 2 and 4 the messages CfS a(d)Ca ON or CfS a(d)Ca ON/CfS a(d)Ca OFF may appear.

Display group 46 -lambda regulation- catalyst diagnosis (catalytic conversion test)
l  Control unit is mode 04 - basic settings l  Vehicle stopped, engine running at fast idle
Read measur. value block 46			→	◂ The display reads
xxxx/min	xxxx °C	xx %	text
1	2	3	4	◂ Display fields	Target value	Analysis
				Result of catalytic conversion test (Test OFF/Test ON/CatF1 OK/CatF1 not OK)	CatF1 OK	--
			Catalytic conversion measurement value		50 % minimum	--
		Catalyst temperature			300 °C minimum	--
	Engine revs				1500...3900/min	--

t	Note on display group 46:

t	Catalytic conversion test conditions: No faults stored in the memory, engine idling, coolant temperature 60...120 °C, lambda regulation active and stable.

Display group 99 -lambda control- operative state lambda control
l  Engine idling
l  Control unit in mode 08 - Read measured value block, lambda control ON
Read measured value block 99			→	◂ Message on the display
xxxx rpm	xxx.x °C	x.x %	text
1	2	3	4	◂ Display fields	Target value	Analysis
				Pre-catalyst lambda control operative state	Reg. λ OFF or Reg. λ ON	---
			Pre-catalyst lambda probe		-10.0...10.0 %	→ Anchor
		Coolant temperature			80.0...110 °C	→ Chapter
	Engine revs (idling revs)				640...930 rpm	→ Anchor