DTC 1231

1. With the ignition "OFF", disconnect the Motronic control unit harness connector. The Motronic control unit is located beneath the drip tray, at the left rear (drivers side) of the engine compartment.
2. Disconnect the high tension ignition lead from the coil and connect it to ground with a jumper wire.
3. Connect a suitable volt/ohm meter between terminal 2 and 35 of the Motronic control unit harness connector. Set the voltmeter to DC volts.

Special Tools:

CAUTION: Avoid damaging the delicate connectors within the control unit harness connector. A simple set of test leads can be fabricated using flat connectors (part # VW N 17 457 2) or equivalent, and a pair of alligator clips.

4. Raise the vehicle.
5. Rotate one front wheel in a forward direction. The opposite wheel must be prevented from rotating.

^ Reading should alternate between 0 and 4 volts DC.

6. If the correct measurement is obtained the problem may be intermittent (check the integrity of the harness and connectors). If the correct reading is not obtained:

a. Check for good ground at terminal 35 of the harness connector.
b. Check the vehicle speed input circuit between the instrument cluster and terminal 2 of Motronic control unit. Refer to CHASSIS ELECTRICAL DIAGRAMS for instrument cluster information.

Vehicle Speed Sensor:

7. If all circuits are OK, repair or replace the vehicle speed sensor or instrument cluster as necessary.