DTC 4431

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. Connect a suitable volt/ohm meter between terminal 17 and 35 of the Motronic control unit harness connector. Set the volt/ohm meter to volts and turn the ignition "ON".

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.

^ The correct measurement should be approx. 12 volts.

If the measurement is correct the problem is intermittent, or the CIS-E Motronic control unit or the idle stabilizer valve may be defective. Check the wiring harness for shorts to ground or 12V. Repair or replace as necessary.
If the measurement is incorrect continue with step 3.

3. Disconnect the idle stabilizer valve harness connector and measure the voltage at terminal 2 of the connector.

^ The correct measurement should be approx. 12 volts.

4. Measure the resistance between terminal 17 of the control unit harness connector and terminal 1 of the idle stabilizer valve harness connector.

^ The correct measurement should be approx. 0 ohms (continuity).

If the correct measurements are not obtained repair or replace the harness as necessary. If the correct measurements are obtained check the resistance of the idle stabilizer valve.

5. Measure the resistance between the two terminals of the idle stabilizer valve.

^ The correct measurement should be approx. 0 ohms (continuity).

If the correct measurement is not obtained replace the idle stabilizer valve. If the correct measurement is obtained the CIS-E Motronic control unit may be defective.