Checking Lambda probe heating for Lambda probe before catalytic converter — VW

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

Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
Test box V.A.G 1598/31
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Adapter set V.A.G 1594

Current flow diagram

Check conditions

Fuse 43 must be OK.
The battery voltage must be at least 11.5 V.
Fuel pump relay must be OK

Test sequence for Lambda probe 1 bank 1

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
01-9
.)

Rapid data transfer
HELP
Select function XX
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, 4 and 1 for "Display group number 41" and confirm entry with Q key.

Read measured value block 42
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

Check the specifications for the Lambda probe heating in display zone 2.

Display zones
1 · 2 · 3 · 4
Display group 41: Lambda probe heating before and after catalytic converter
Display · --- · Htg.bC.ON / / Htg.bC.OFF · --- · Htg.aC.ON / / Htg.aC.OFF
Indicated · --- · Lambda probe heating before catalytic converter ON / or / Lambda probe heating before catalytic converter OFF · --- · Lambda probe heating after catalytic converter ON / or / Lambda probe heating after catalytic converter OFF
Specification · --- · Htg.bC.ON / Htg.bC.OFF / (occasionally alternating) · --- · ---

Note:

The Lambda probe heating may be switched ON or OFF depending on the operating conditions of the engine, therefore the display in display zone 2 may show "Htg.b(a)C.ON" or alternating from "Htg.b(a)C.ON" to Htg.(b)aC.OFF".

If the specifications are not obtained:

Press ⇒key.
Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
Switch off ignition.
Remove protective cover from vehicle underbody and separate 6-pin connector (black) -1- to Lambda probe before catalytic converter (G39).

Set multimeter to measure resistance and check resistance of probe heating at Lambda probe connector contacts 3+4.
Specification: 2.5...10.0 ω

If it is determined that probe heating has an open circuit:

Replace the Lambda probe before catalytic converter (G39).

If the Lambda probe is renewed, the learnt values in the engine control unit must be erased => Page
24-139

If probe heating has continuity:

Checking voltage supply

Connect multimeter using aux. cables from V.A.G 1594 to measure voltage at contacts 3 and 4 (connector to engine control unit).
Start engine and run at idling speed.
Measure voltage supply and observe the display group 42, display zone 2.
Display, Htg.bC.ON:
Specification: 11.0...14.5 V
Display, Htg. bC.ON/Htg.bC.OFF (alternating):
Specification: Between 0.0...12.0 V fluctuating
Switch off ignition.

If no voltage is present:

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 6-pin connector according to current flow diagram.
Contact 4 + socket 5
Wire resistance: Max. 1.5 ω

If the specification is obtained:

Check wire for open circuit between 6-pin connector contact 3 and fuel pump relay (J17) using current flow diagram.
Wire resistance: max. 1.5 ω