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

Checking lambda probe wiring

–	Unscrew protective cover -arrows- on vehicle floor.

–	Unplug 6-pin connector (black) -1- for lambda probe upstream of catalytic converter -G39-.

–	Connect test box -V.A.G 1598/31- to wiring harness for engine control unit. Do not connect engine control unit → Chapter.

–	Check for open circuit in the following wiring connections:

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

–	Check for shorts between the two wires.

If no wiring fault is detected:

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