Audi Workshop Service and Repair Manuals > A3 Mk1 > Power unit | Motronic injection and ignition system (4-cylinder turbo) | Mixture preparation system, electronic inj.,Gas | Servicing Motronic injection system | Checking Lambda probe and Lambda control before catalytic converter

Checking Lambda probe wiring

–	Unplug the 6-pin connector (black) to the Lambda probe -G39-.

–	Connect the test box -V.A.G 1598/31- to the wiring harness to the engine control unit, but do not connect the actual engine control unit → Chapter.

–	Check for open circuit in the following wiring.

–	Eliminate open circuit in wiring if necessary. → Current flow diagrams, Electrical fault finding and Fitting locations

–	Check the wiring for mutual short circuit.

If the wiring is OK:

–	Replace the engine control unit → Chapter.