Checking lambda probe heating for lambda probe after catalytic converter — AUDI

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
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Adapter set V.A.G 1594
Current flow diagram

Check conditions

Fuses for lambda probe must be OK.

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

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

Test sequence

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
01-13
.)

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
HELP
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 41
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

Check status of lambda probe heating after catalytic converter in display zone 4:
Display: Htg.aC.ON

Note:

The lambda probe heating may be switched on or off depending on the operating mode of the engine, therefore the display in display zone 4 may show "Htg.aC.ON or alternating from Htg.aC.ON to Htg.aC.OFF.

If the specification is not obtained:

Unplug 4-pin connector to lambda probe (G130) -2-. Fitting location: electronics box in left footwell.
Lift up floor mat in left footwell:

=> General body repairs, Interior; Repair group 70; Removing and installing floor mats
General body repairs, Interior
Removing and installing floor mats

Remove screws -arrows- securing cover.
Take off cover.

Check probe heating for continuity at lambda probe connector contacts 1 and 2.

Note:

The heater element resistance is approx. 1...5 ω at room temperature. Even slight increases in room temperature increase the resistance greatly.

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

Renew the lambda probe after catalytic converter (G130).

If probe heating has continuity:

Connect multimeter using aux. cables from V.A.G 1594 to measure voltage at contacts 1+2 (connector to engine control unit).
Start engine and run at idling speed.
Measure the voltage supply:
When display group 41, display zone 4 displays
Display, Htg.aC.ON:
Specification: 11.0...14.5 V
Display, Htg. aC.ON/Htg.aC.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 => Page
24-8
.

Check wiring for open circuit between 4-pin connector contact 2 and socket 63
Wire resistance: Max. 1.5 ω

If the specification is obtained:

Check wire between 4 pin connector contact 1 and fuel pump relay (J17) for open circuit using current flow diagram.
Wire resistance: max. 1.5 ω