Cruise Control Servo: Testing and Inspection

Speed Control Servo

For complete speed control system diagnosis, refer to the appropriate Powertrain Diagnostic Procedures. To test the speed control servo only, refer to the following:

The engine must be started and running for the following voltage tests.
1. Start engine.
2. Disconnect 4-way electrical connector at servo.
3. Turn speed control switch to ON position.

Fig. 4 Servo Harness Connector:

4. Check for battery voltage at pin-3 of wiring harness 4-way connector. This is the 12 volt feed from the stoplamp switch. When the brake pedal is depressed, voltage should not be present at pin-3. If voltage is not present with brake pedal not depressed, check for continuity between servo and stop lamp switch. Also check stop lamp switch adjustment.
5. Connect a small gauge jumper wire between the disconnected servo harness 4-way connector pin-3, and pin-3 on the servo. Check for battery voltage at pins-1, 2 and 4 of the servo. If battery voltage is not at these pins, replace the servo.
6. Turn ignition switch to OFF position. Check for continuity between disconnected servo harness 4way connector pin4 and a good ground. There should be continuity. If not OK, repair open circuit to ground as required.