Checking Lambda probe and Lambda regulation before catalyst — VW

AUR
Note:

Only gold-plated contacts must be used to repair the contacts in the Lambda probes connectors.

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Fault reader V.A.G 1551 (or vehicle system tester V.A.G 1552) with cable V.A.G 1551/3
Adapter set V.A.G 1594

Test box V.A.G 1598/31
Current flow diagram

Check conditions

The fuses 1, 3, 31, 34, 36 and 40 must be OK.
The battery voltage must be at least 11.5 V.
Earth connection in plenum chamber OK.
All electrical consumers, e.g. lights and rear window heating must be switched off.
If the vehicle is equipped with an air conditioning system, this must be switched off.
Exhaust system between catalyst and cylinder head must be free of leaks
No faults must be stored in fault memory => Page
01-20
, interrogating and erasing fault memory.
Coolant temperature must be at least 80 °C, =>display group 01, display zone 2.
Once started, the engine should only be run at idling speed. This allows the interference variable of the exhaust emissions test to be applied and prevents the coolant temperature sender from entering a fault in the fault memory.

Wait at least 60 seconds before disconnecting the 4-pin connector from coolant temperature sender (G62).

Functional check

Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
(Connecting fault reader and selecting engine control unit => Page
01-8
.)

Rapid data transfer
HELP
Select function XXX
Indicated on display:

Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

Read measured value block
Input display group number XXX
Indicated on display:

Press keys 0, 0 and 1 for "Display group number 1" and confirm entry with Q key.

Read measured value block 1
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

Check whether the coolant temperature is above 80 °C in display zone 2.
Change to display group 30 as follows:
Press C key.

Read measured value block
Input display group number XXX
Indicated on display:

Press keys 0, 3 and 0 for the "Display group number 30" and confirm entry with Q key.

Read measured value block 30
⇒
1
2
Indicated on display:
(1...2 = Display zones)

Check status of Lambda regulation before catalyst (display zone 1):
Specification: 111

Significance of numbers in 3-digit number block
=> Page
01-137
.

If the specification is not obtained:

Check Lambda probe heating before catalyst
=> Page
24-33
.

If the specification is obtained:

Change to display group 32 as follows:
Press C key.
Press keys 0, 3 and 2 for "Display group number 32" and confirm entry with Q key.

Read measured value block 32
⇒
1
2
Indicated on display:
(1...2 = Display zones)

Check Lambda learnt values at idling speed (additive) in display zone 1.
Specification: -15.0...15.0 %
Check Lambda learnt values at part load (multiplicative) in display zone 2.
Specification: -20.0...20.0 %

If the specifications are not obtained:

Press ⇒key.
Press keys 0 and 6 for the "End output" function and confirm input with the Q key.
Switch off ignition.
=>Page
01-140
, Evaluating display group 32

If the specifications are obtained:

Change to display group 33 as follows:
V.A.G 1551: Press key 3
V.A.G 1552: Press key ↑

Read measured value block 33
⇒
1
Indicated on display:
(1= Display zones)

Check Lambda regulation in display zone 1. The display should fluctuate slightly in the range of
-10.0...10.0 %.

If the display in display zone 1 remains at a constant value:

Press ⇒key.
Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
Switch off ignition.
Check basic voltage of Lambda probe before catalyst => Page
24-102
.
Check Lambda probe wiring for Lambda probe before catalyst
=> Page
24-103
.

If display fluctuates in display zone 1:

Pull the 4 pin connector off coolant temperature sender (G62) with coolant temperature gauge sender (G2) -arrow-.

Note:

This test will only function if the engine has been running for at least 60 seconds at idling speed only. Once the connector has been disconnected, various component diagnostics and the Lambda regulator are electronically locked for 20 seconds. The fuel/air mixture is made richer and the Lambda probe has to recognise this with an increased display value.

Observe Lambda regulation in display zone 1:
The display must fall and then be corrected back to the specifica
tion range
-10.0...10.0 % within 60 seconds.

If the specification is not obtained:

Reconnect 4-pin connector from coolant temperature sender (G62).
Press ⇒key.
Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
Carry out a test drive to remove possible residue on Lambda probe and repeat check.

Observe the valid safety precautions when carrying out a road test => Page
24-29
.

If specification is not reached following a test drive:

Renew Lambda probe before catalyst (G39)
=>Page
24-3
, item
8
.
Interrogate fault memory, if necessary, repair any faults and then erase fault memory => Page
01-20
, interrogating and erasing fault memory.
Erase the learnt values and adapt the engine control unit again=> Page
24-132
.

If the specification is obtained:

Reconnect 4-pin connector to coolant temperature sender (G62) immediately.
Observe Lambda regulation in display zone 1 again:
The display must rise and then be corrected back to the specifica
tion range
-10.0...10.0 % within 60 seconds.
Press ⇒key.
Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
Switch off ignition.

Checking basic voltage of Lambda probe before catalyst

Separate 6-pin connector (black) to Lambda probe before catalyst (G39) -arrow-.

Connect multimeter with aux. cables from V.A.G 1594 to measure voltage at contacts 1 + 5 (connector to engine control unit).
Switch on ignition and measure basic voltage.
Specification: 0.40...0.50 V
Switch off ignition.

If the specification is not obtained:

Check Lambda probe wiring for Lambda probe before catalyst
=> Page
24-103
.

If the specification is obtained:

Renew Lambda probe before catalyst (G39)
=>Page
24-3
, item
8
.
Interrogate fault memory, if necessary, repair any faults and then erase fault memory => Page
01-20
, interrogating and erasing fault memory.
Erase the learnt values and adapt the engine control unit again=> Page
24-132
.

Checking Lambda probe wiring for Lambda probe before catalyst

Remove left cover for plenum chamber.
Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.

Separate 6-pin connector (black) to Lambda probe before catalyst (G39) -arrow-.

Check wiring for open circuit between test box and 6-pin connector to control unit referring to current flow diagram.
Contact 1 and test box socket 14
Contact 2 and test box socket 15
Contact 5 and test box socket 34
Contact 6 and test box socket 33
Wire resistance: max. 1.5 ω
Check wiring on 6-pin connector additionally for short to one another.
Specification: ∞ω

If no fault is detected in the wiring:

Renew Lambda probe before catalyst (G39)
=>Page
24-3
, item
8
.
Interrogate fault memory, if necessary, repair any faults and then erase fault memory => Page
01-20
, interrogating and erasing fault memory.
Erase the learnt values and adapt the engine control unit again=> Page
24-132
.