Audi Workshop Service and Repair Manuals

Special tools, testers and auxiliary items

• ◆ Hand multimeter V.A.G 1526 or V.A.G 1526 A
• ◆ Adapter set V.A.G 1594

• ‒ The lambda probe heating circuit is monitored by the self-diagnosis system.
• ‒ Interrogate fault memory.
• ‒ → Unbolt protective cover for lambda probe connector on right-hand side under floor panel.
• ‒ Unplug 4-pin connector for lambda probe -G39.

• ‒ → Test for open circuit (measure resistance) by connecting V.A.G 1526 between contacts 1 and 2 of the lambda probe plug 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.
• ‒ → If the fuse is OK, connect diode test lamp V.A.G 1527 between engine earth and contact 1 of plug on wiring harness.
• ‒ 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.
• ‒ Test for open circuit in wiring between contact 2 of plug on wiring harness (earth wire) and contact 27 on the engine control unit. Rectify any open circuits.
• ‒ If both the fuse and the wiring are OK but the diode test lamp still does not light up, test the fuel pump relay .