Checking Lambda probe and Lambda regulation after catalytic converter — VW

BFS
Notes:

Only gold plated contacts may be used when servicing Lambda probe connector contacts 3 and 4.
The Lambda regulation after catalytic converter is master of the Lambda regulation before catalytic converter and serves as a corrective regulation.

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

Test prerequisites

All fuses must be OK.
The battery voltage must be at least 11.5 V.
All electrical consumers, e.g. lights and rear window heating must be switched off.
If the vehicle is equipped with air conditioning, this must be switched off.
Exhaust system between catalytic converter and cylinder head must be free of leaks
No faults must be stored in fault memory => page
01-21
, Interrogating and erasing fault memory.
Coolant temperature must be at least 80 °C, =>display group 04, display zone 3.

Functional check

Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit.
(Connecting fault reader and selecting engine control unit => page
01-11
).

Rapid data transfer
HELP
Select function XX
Indicated on display:

Press keys 0 and 4 for function "Initiate basic setting" and confirm entry with Q key.

Basic setting
Input display group number XXX
Indicated on display:

Press keys 0, 4 and 3 for "Display group number 43" and confirm entry with Q key.

System in basic setting 43
⇒
1
2
3
4
Indicated on display:
(1...4 = display zones)

Models ▸05.01

Raise engine speed to 2500...4500 rpm until the display in
display zone 4 jumps from "Test OFF" to "Test ON".

Note:

This process can take several minutes.

Allow engine to continue to run at increased revs until
display zone 4 displays the result of the test:
Specification "B1 P2 OK."

Models 05.01 ▸

Depress brake pedal and hold.
Depress accelerator down to full throttle position.

Engine speed will be increased by engine control unit to
approx. 3000 rpm.

When the diagnosis is initiated by the engine control unit, the display in display zone 4 jumps from "Test OFF" to "Test ON"

Note:

This process can take several minutes.

Leave brake and accelerator depressed until the result of functional test is displayed in display zone 4:
Specification "B1 P2 OK."

Continuation for all models:

If "B1 P2 n.OK." is displayed:

Check Lambda probe voltage in display zone 3.
The voltage must be in range of
0.00...1.00 V fluctuating.

If the specification is obtained:

Press the ⇒key.
Press keys 0 and 6 for function "End output" and confirm entry with the Q key.
Switch off ignition.
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
24-27
.

If "B1 P2 n.OK." is displayed again:

Replace Lambda probe after catalytic converter (G130).
Interrogate fault memory, repair faults if necessary and then erase fault memory => page
01-21
, Interrogating and erasing fault memory.
Erase learnt values and adapt engine control unit=> page
24-134

If the display in display zone 3 remains constantly at a value:

Continue check according to following table.

Display · Cause · Continuation of check
Between 0.390... / 0.500 V · Open circuit
1.105 V · Short to positive · => page 24-103 / Checking Lambda probe wiring
0.000 V · Short to earth

Checking basic voltage

Unscrew protective cover on underbody -arrows- and disconnect 4-pin connector (brown) -1- to Lambda probe after catalytic converter (G130).

Connect multimeter to measure voltage at contacts 3 and 4 (connector to engine control unit) using adapter cables from V.A.G 1594.
Start engine and measure basic voltage.
Specification: 0.39..0.00.50 V
Switch off ignition.

If the specification is not obtained:

Check Lambda probe wiring
=>page
24-103
.

If the specification is obtained:

Replace Lambda probe after catalytic converter (G130).

Erase learnt values and adapt engine control unit=> page
24-134

Checking Lambda probe wiring, Lambda probe 2

Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.

Check wiring for open circuit between test box and 4-pin connector to engine control referring to current flow diagram.
Contact 3 and test box socket 35
Contact 4 and test box socket 16
Wire resistance: max. 1.5 ω
Additionally check wiring at 4-pin connector for short to one another.
Specification: ∞ω

If no wiring fault is detected:

Renew engine control unit => page
24-126
.