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

Requirements for test:

• ● 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 4-pin connector (brown) for lambda probe (after catalytic converter) -G130.

Note:

For access to connector, unscrew bolts securing coolant expansion tank and pivot expansion tank clear to the side. The coolant hoses do not have to be disconnected.

• ‒ → Connect multimeter (resistance measurement range) between contacts 1 and 2.
• ‒ Specification: 2 ... 15ω(at room temperature)

If the specification is not attained:

• ‒ Replace the lambda probe (after catalytic converter) -G130.

If the specification is obtained:

• ‒ Test voltage supply for lambda probe heating.

Testing voltage supply for lambda probe heating

• ‒ → Connect multimeter (voltage measurement range) between contacts 1 (positive) and 2 (earth).
• ‒ Start the engine.
• ‒ Specification: approx. battery voltage

Note:

If required, observe Display Group 041, display zone 4 in the "Read measured value block" function to find out when the engine control unit is switching the lambda probe heating on and off.

If no voltage is present:

• ‒ → Connect multimeter (voltage measurement range) as follows:

• ‒ Operate starter briefly.
• ‒ Specification: approx. battery voltage

If there is still no voltage reading:

• ‒ Test for open circuit in wiring connection between fuel pump relay and contact 1 on connector via fuse:

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

If the voltage supply is OK:

• ‒ → Connect multimeter (voltage measurement range) as follows:

• ‒ Start the engine.
• ‒ Specification: approx. battery voltage (may fluctuate)
• ‒ Switch off ignition.

If no voltage is present:

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

• ‒ → Test for open circuits in the following wiring connection:

• ‒ Rectify any open circuits.

If the wiring connection is O.K. but the lambda probe heating still has no earth connection:

• ‒ Fit a new engine control unit => Page 24-13.