SEAT Workshop Service and Repair Manuals

Analysis measurement value blocks, display groups 30...49, 99 -lambda regulation-

Display group 30 -lambda regulation-
l  Engine idling
Read measurement value block 30			→	← The display reads:
xxx	xxx	---	---
1	2	3	4	← Display fields	Target value	Analysis
		State of the post-catalyst lambda regulation l  Catalyst temperature min. 400.0 °C → Anchor			110	→ Anchor
	State of the pre-catalyst lambda regulation				111	→ Anchor

Notes on display fields 1 and 2:

t	The first position of the 3-digit numerical block switches temporarily from 0 to 1 and vice versa (lambda probe heating ON and OFF).

t	Depending on the state of lambda regulation, the 3-digit numerical may be 0 or 1 intermittently.

t	The bits in the display field 1 and 2 will not change to 1 until the catalyst temperature is above 400.0 °C → Anchor.

t	The third bit in display field 2 only changes to 1 when the engine is running at half load (2500-4000 rpm).

Meaning of the figures in the 3-digit numerical block, display fields 1 and 2 - state of the pre- and post-catalyst lambda regulation

Meaning if digits = 1
1	2	3	Meaning
		1	Lambda regulation active
	1		lambda probe ready
1			Lambda probe heating ON

Display group 32 -lambda regulation-, pre-catalyst lambda self-adaptation values
l  Engine idling
Read measurement value block 32			→	← The display reads:
xx.x %	xx.x %	---	---
1	2	3	4	← Display fields	Target value	Analysis
		Pre-catalyst lambda self-adaptation value at half load (multiplicative)			-10.0...10.0 %	→ Anchor
	Pre-catalyst lambda self-adaptation value at idling (additive)				-10.0...10.0 %	→ Anchor

Notes on display fields 1 and 2:

t	Low values: the engine runs on an overly rich mix, so the lambda regulation makes the mix leaner.

t	High values: the engine runs on an overly lean mix, so the lambda regulation enriches the mix.

t	When the control unit lacks voltage, all the self-adaptation values are reinitialised.

t	addi. = additive - The fault (e.g. infiltrated air) loses importance as engine revs increase. In the case of the additive self-adaptation value, the injection timing is modified according to a fixed magnitude that does not depend on basic injection timing.

t	mul. = multiplicative - The fault (e.g. faulty injector) gains importance as engine revs increase. In the case of the multiplicative self-adaptation value, there is a percentile change in injection timing that depends on basic injection timing.

Start the self-adaptation process: control unit in mode 04, basic settings.

t	Conditions for self-adaptation for idling: idling; coolant temperature 75 °C min; intake air temperature 90 °C max.

t	Conditions for self-adaptation for half load: coolant temperature 75 °C min; intake air temperature 90 °C max.

Analysis display group 32, display fields 1 and 2 - pre-catalyst lambda self-adaptation values

The display reads	Possible cause of the fault	Elimination of the fault
Low lambda self-adaptation values	t  Low self-adaptation values at idling, being normal the self-adaptation values at half load: possibility of diluted oil (high fuel content in oil)	–  Disappears in motorway driving or when oil is changed.
	t  Leaky injector	–  Test the injector → Chapter.
	t  Fuel pressure very high	–  Test the fuel pressure regulator and retaining pressure → Chapter.
	t  Fuel tank ventilation solenoid valve on the activated charcoal filter always open	–  Test the activated charcoal filter solenoid valve → Chapter.
	t  Lambda probe heating faulty or lambda probe dirty	–  Test the pre-catalyst lambda probe heating → Chapter.

The display reads	Possible cause of the fault	Elimination of the fault
High lambda self-adaptation values	t  High self-adaptation values at idling, being less high the self-adaptation values at half load: possibility of infiltrated air in the upper part of the intake manifold	–  Test the intake system for leakage → Chapter.
	t  Injector clogged	–  Test the injector → Chapter.
	t  Fuel pressure very low	–  Test the fuel pressure regulator and retaining pressure → Chapter.
	t  Infiltrated air in the exhaust manifold gasket
	t  Lambda probe heating faulty or lambda probe dirty	–  Test the pre-catalyst lambda probe heating → Chapter.

Display group 33 -lambda regulation-, pre-catalyst lambda self-adaptation values
l  Engine idling
Read measurement 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			1.000...2.000 V	---
	Pre-catalyst lambda probe regulator				-10.0...10.0 %	→ Anchor

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 regulation to control due to a fault in lambda regulation. Consult the fault memory → Chapter.

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

The display reads	Possible cause of the fault	Elimination of the fault
Outside tolerance	t  Negative limit: engine very rich, the lambda regulation makes the mix leaner t  Positive limit: engine very lean, the lambda regulation enriches the mix	–  Wait 30 seconds for the value displayed to stabilise.
	t  Infiltrated air	–  Test the intake system for leakage → Chapter.
	t  Injector faulty	–  Test injector → Chapter.
	t  Lambda self-adaptation values, at limit	–  Check lambda self-adaptation values in display group 32.

Display group 34 lambda regulation - diagnosis pre-catalyst lambda probe (ageing test via amplitude ratio)
l  Control unit in mode 04 - Basic settings
–  Depress the brake pedal
l  Vehicle stopped, engine running at fast idle
Read measurement value block 34			→	← The display reads:
xxxx rpm	xxx.x °C	x.xx	text
1	2	3	4	← Display fields	Target value	Analysis
				Results the pre-catalyst lambda probe ageing test (Test OFF/Test ON/F1-S1 OK/ F1-S1 not OK)	F1-S1 OK	---
			Pre-catalyst lambda probe amplitude ratio		0.70... 2.00	---
		Catalyst temperature			min. 400.0 °C	---
	Engine revs				1200...1400 rpm	---

Note on display field 2:

t	Value calculated based on engine revs and load.

Display group 36 -lambda regulation-, post-catalyst
l  Control unit in mode 04 - Basic settings
–  Depress the brake pedal
l  Vehicle stopped, engine running at fast idle
Read measurement value block 36			→	← The display reads:
x.xxx V	text	---	---
1	2	3	4	← Display fields	Target value	Analysis
						---
					---	---
		Test post-catalyst lambda probe (Test ON/Test OFF/F1-S2 OK/F1-S2 not OK)			F1-S2 OK	---
	Post-catalyst lambda probe voltage				0.000...1.000 V	→ Anchor

Notes on display field 1:

t	The voltage signal “rich mix (low residual oxygen)” is at approx. 0.700...0.900 V.

t	The voltage signal “lean mix (high residual oxygen)” is at approx. 0.000...0.300 V.

t	In changing from “rich” to “lean” and vice versa (λ = 1.0) voltage jumps from 0.700...0.900 V to 0.000...0.300 V or vice versa.

t	Due to the large jump in voltage, the lambda regulation cannot hold constant the ideal mix corresponding to λ = 1.0. The regulation oscillate between the states “somewhat lean” and “somewhat rich”.

t	The value display should hold momentarily below 0.300 V and above 0.600 V. Values below 0.450 V mean “lean” and those above 0.450 V, “rich”.

Lambda probe voltage Uλ in mV A: High lambda probe voltage t  Rich mix (excess fuel or lack of air) t  High CO value B: Low lambda probe voltage t  Lean mix (lack of fuel or excess air) t  Low CO value Analysis display group 36, display field 1 - post-catalyst lambda probe voltage

The display reads	Possible cause of the fault	Elimination of the fault
Constant 1.085 V	t  Short circuit to positive by: lambda probe, probe wire, earth wire, engine control unit	–  Test basic voltage of lambda probe 2 → . –  Test the wiring of lambda probe 2 → .
Constant between 0.400...0.500 V	t  Open circuit by: lambda probe, probe wire, earth wire, engine control unit
Constant 0.000 V	t  Short circuit to earth by: lambda probe, probe wire, earth wire, engine control unit

Display group 37 -lambda regulation-, lambda probes
l  Vehicle stopped, engine running at fast idle
l  Control unit in mode 04 - Basic settings
Read measurement value block 37			→	← The display reads:
xx.x %	x.xxx V	xxx.xxx	text
1	2	3	4	← Display fields	Target value	Analysis
				Test of lambda probes (Test ON/ Test OFF/Syst. OK/Sys. not OK)	Sys. OK	---
			Irrelevant for Technical Assistance		---	---
		Lambda probe voltage Post-catalyst lambda probe			0.000...1.000 V	→ Anchor
	Engine load				15.0...30.0 %	→ Anchor

Display group 41 -lambda regulation-, lambda probe heating
l  Engine idling
Read measurement value block 41			→	← The display reads:
---	text	---	text
1	2	3	4	← Display fields	Target value	Analysis
				Post-catalyst lambda probe heating	CfS dCa ON CfS dCa OFF	---
		Pre-catalyst lambda probe heating			CfS aCa ON CfS aCa OFF	---

Depending on engine load state, the lambda probe heaters are activated or deactivated, i.e. display fields 2 and 4 may read CfS a(d)Ca ON or, alternatively, CfS a(d)Ca ON/CfS a(d)Ca OFF.

Display group 46 -lambda regulation- catalyst diagnostic (catalytic conversion test)
l  Control unit in mode 04 - Basic settings
–  Depress the brake pedal
l  Vehicle stopped, engine running at fast idle
Read measurement value block 46			→	← The display reads:
xxxx rpm	xxx.x °C	x.xx	text
1	2	3	4	← Display fields	Target value	Analysis
				Result of catalytic conversion test (Test OFF/Test ON/Cat F1 OK / Cat F1 not OK)	Cat F1 OK	---
			Amplitude ratio		0.00...0.50	---
		Catalyst temperature			400.0 °C minimum	---
	Engine revs				1200...1400 rpm	---

Display group 99 -lambda regulation-, lambda regulation operational state
l  Engine idling
l  Control unit in mode 04 - Basic settings, lambda regulation OFF
l  Control unit in mode 08 - Read measurement value block, lambda regulation ON
Read measurement value block 99			→	← The display reads:
xxxx rpm	xxx.x °C	xx.x %	text
1	2	3	4	← Display fields	Target value	Analysis
				Operational state of the pre-catalyst lambda regulation	Reg. λ OFF or reg. λ ON	---
			Pre-catalyst lambda regulator		-10.0...10.0 %	→ Anchor
		Coolant temperature			80.0...110.0 °C	→ Anchor
	Engine revs (idling revs)				810...890 rpm	→ Anchor

Notes on display field 4:

t	For defined fault finding, the lambda regulation is deactivated when display group 99 is selected in function “Basic settings” and is activated in “Read measurement value block”. When function 04 “Basic settings” is abandoned, the regulation is automatically reactivated.

t	Pressing 4 and 8 on the -V.A.G 1551/1552- switches between function 04 “Basic settings” and function 08 “Read measurement value block”.