Checking Lambda probe heating before catalyst: Audi 1.6 (BAH)

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 1598/22
Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
Adapter set V.A.G 1594
Current flow diagram

Check conditions

The fuses 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
01-7
.)

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.

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:

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
13
.

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:

Connect test box V.A.G 1598/22 to control unit wiring harness
=> Page
24-121
.

Check wires between test box and 4-pin connector (connector to control unit) for open circuit using current flow diagram.
Contact 2+socket 13
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