Audi Workshop Service and Repair Manuals

Special tools and workshop equipment required

• ◆ V.A.G 1526 A
• ◆ V.A.G 1594 A
• ◆ V.A.G 1598/31

Test requirements:

• ● Coolant temperature at least 80 °C.
• ● Fuse for Lambda probe heating OK.

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

Test sequence

• ‒ Unplug 6-pin connector (black) to lambda probe upstream of catalytic converter -G39.

• ‒ → Connect multimeter between contacts 3 and 4 to measure resistance.
• ‒ Specified value at room temperature 2.5 ... 10 ω

If specified value is not attained:

• ‒ Replace the lambda probe 1 upstream of catalytic converter.
  -G39.

If specified value is attained:

• ‒ Checking the voltage supply to the Lambda probe heating.

Checking voltage supply for lambda probe heating

• ‒ → Connect multimeter between contacts 3 and 4 to measure voltage.
• ‒ Start the engine.
• ‒ Specified value: approx. battery voltage

Note:

Points at which Lambda probe heating is switched on and off by engine control unit can be observed in "Reading measured value block" function, display group number 041 and display zone 2.

If no voltage is present:

• ‒ → Connect multimeter as follows to measure voltage.

• ‒ Operate starter briefly.
• ‒ Specified value: approx. battery voltage

If no voltage is present:

• ‒ Checking the wiring from contact 3 on the connector via the fuse to the fuel pump relay for an open circuit:

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

If voltage supply is OK:

• ‒ → Connect multimeter as follows to measure voltage:

• ‒ Start the engine.
• ‒ Specified value: approx. battery voltage

Note:

Points at which Lambda probe heating is switched on and off by engine control unit can be observed in "Reading measured value block" function, display group number 041 and display zone 2.

• ‒ Switch ignition off.

If no voltage is present:

• ‒ Connect test box V.A.G 1598/31 to wiring harness for engine control unit; do not connect the engine control unit .

• ‒ → Checking for open circuit in the following wiring connections:

• ‒ Rectify open circuit, if necessary.

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

If wiring is OK but there is no earth connection for the Lambda probe heating:

• ‒ Replace engine control unit => Page 24-32.