Audi Workshop Service and Repair Manuals

• ‒ The lambda probe heating circuit is monitored by the self-diagnosis system.
• ‒ Interrogate fault memory .
• ‒ Unplug 4-pin connector for lambda probe.
  Fitting location => Page 24-5.
• ‒ → Use V.A.G 1526 to measure resistance between contacts 1 and 2 on lambda probe connector.

Note:

The resistance of the heating element at room temperature is approx. 1...5 ω. With even a small temperature rise this value will increase sharply.

• ‒ If an open circuit is detected, fit a new lambda probe.

If the heating element has continuity, test the power supply for the lambda probe heating as follows:

• ‒ Test fuse for lambda probe heating.

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

• ‒ → If the fuse is OK, connect diode test lamp V.A.G 1527 between engine earth and contact 1 of wiring harness connector.
• ‒ Operate the starter briefly (the engine can be allowed to start briefly). The diode test lamp should light up.

• ‒ → If diode test lamp does not light up, test for open circuit or short to earth in wiring between fuse and contact 1 of plug on wiring harness. Rectify open/short circuit if necessary.

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

• ‒ If both the fuse and the wiring are OK but the diode test lamp still does not light up, test the fuel pump relay => Page 24-33.
• ‒ Switch off ignition.
• ‒ Connect test box V.A.G 1598/22 to wiring harness for control unit
  .

• ‒ → Test for open circuit in wiring between contact 2 on 4-pin wiring harness connector (earth connection via engine control unit) and contact 27 on engine control unit. If necessary, rectify open circuit.
• ‒ If all the test results obtained so far have been OK, fit a new engine control unit
  .