Speedometer & Odometer Do Not Operate Properly
- Unplug VSS buffer, located under passenger side end of instrument panel. Turn ignition on. Check for battery voltage between harness connector Pink/Black wire and ground. If battery voltage exists, go to next step. If battery voltage does not exist, repair short or open in Pink/Black wire.
- Check for battery voltage between Pink/Black wire and Black/White wire at harness connector. If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Black/White wire.
- Raise and support vehicle with drive wheels off ground. Start engine. Shift transmission to Drive. Check for AC voltage between Purple/White and Light Green/Black wires of harness connector.
- Voltage should change as wheel speed increases or decreases. If AC voltage does not exist, check for short or open in Purple/White and Light Green/Black wires. If wiring is okay, replace vehicle speed sensor.
- Turn ignition off. Reconnect VSS buffer. Start engine. Put transmission into gear. Backprobe Blue/Black and Black/White wires at VSS buffer connector. If AC voltage varies with RPM change, replace VSS buffer.
- Backprobe Red/White and Black/White wires at VSS buffer connector. If AC voltage varies with RPM change, replace VSS buffer. If all foregoing checks are okay, replace instrument cluster.
Courtesy of GENERAL MOTORS CORP.