Checking Lambda probe heating before catalyst — VW

AKP ALD AUC AUD
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 1551/3A
Test box V.A.G 1598/22
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715

Adapter set V.A.G 1594
Current flow diagram

Check conditions

Fuse No. 1 must be OK.
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
01-9
.)

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, 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 before catalyst in display zone 2:
Display: Htg.bC.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 2 may show "Htg.bC.ON or alternating from Htg.bC.ON to Htg.bC.OFF.

If the specification is obtained:

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

If the specification is not obtained:

Only engines which conform to EU 4 standard (engine code AKP, AUC, AUD)

Engines conforming to MVEG II standard (engine code AKK, ALD) => Page
24-39
.

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

Checking voltage supply

Connect the Multimeter with aux. cables from V.A.G 1594 to measure voltage on contacts 3 + 4 (connector to engine control unit).
Start engine and run at idling speed.
Measure the voltage supply:
When display group 41, display zone 2 displays
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
Press ⇒key.
Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
Switch off ignition.

If no voltage is present:

Remove wiper arms and cowl panel:

=> Electrical system; Repair group 92; windscreen wiper system; removing and installing windscreen wiper system
Electrical system
windscreen wiper system
removing and installing windscreen wiper system

Connect test box V.A.G 1598/22 to control unit wiring harness.

Check wire between test box and 6-pin connector (connector to control unit) for open circuit using current flow diagram.
Contact 4+socket 1
Wire resistance: max. 1.5 ω

If the specification is obtained:

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

Only engines conforming to MVEG II standard (engine codes AKK, ALD)

Separate 4-pin connector (black) to Lambda probe before catalyst (G39) -arrow-.

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 Lambda probe before catalyst (G39)
=>Page
24-4
, item
16
.

If probe heating has continuity:

Checking voltage supply

Set multimeter to "Voltage measurement" range.
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.
Specification: 11.0...15.0 V
Switch off ignition.

If no voltage is present:

Check wiring between 4 pin connector contact 2 and engine earth for open circuit
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