Control Switch/Circuit Check
- Disconnect cruise control unit wiring harness connector. Connect voltmeter leads to terminals No. "5" and "8". Turn control switch to ON position. Drive vehicle 20 MPH. If 12 volts are present, go to next step. If no voltage is present, replace control switch or repair open circuit.
- Turn ignition off. Connect ohmmeter leads to terminals No. 8 and 10. Turn control switch to RES position. If resistance is zero ohms, go to next step. If resistance is infinite ohms, replace control switch or repair open circuit.
- With ignition off, connect ohmmeter leads to terminals No. "4" and "8". Turn control switch to FIX/SET position. If resistance is zero ohms, go to next step. If resistance is infinite ohms, replace control switch or repair open circuit.
- Switch/Vent Valve Check
With ignition off, connect ohmmeter leads to terminals No. 5 and 11. Turn control switch to ON position. If resistance is zero ohms, go to next step. If resistance is infinite ohms, replace control switch, brake pedal vent valve or repair open circuit.
- With ignition off, leave ohmmeter leads connected to terminals No. 5 and 11. Leave control switch set to ON position. Apply brake pedal. If resistance is infinite ohms, go to next step. If resistance is zero ohms, replace brake pedal vent valve.
- Vacuum Pump Motor Check
Turn ignition on. Using jumper wire, connect terminal No. 6 to ground. Using jumper wire, apply battery voltage to terminal No. 7. If motor operates, go to next step. If motor does not operate, replace vacuum pump or repair open circuit.
- Vent Valve Check
Turn ignition on. Using jumper wire, apply battery voltage to terminal No. 7. Using jumper wire, repeatedly touch and remove terminal No. 12 to ground. If vent valve does not click, replace vacuum pump or repair open circuit. If vent valve clicks, check control unit, connector pin terminals and wiring harness connector. Repair or replace as necessary.
Courtesy of AUDI OF AMERICA, INC.