Pinpoint Test D - Set Speed Fluctuates
WARNING:
Disable air bag system before working around steering column or removing any air bag system component. See the article AIR BAG RESTRAINT SYSTEM
in the ACCESSORIES/SAFETY EQUIPMENT section.
- Test drive vehicle at a constant speed between 40 and 55 MPH. Check speedometer for constant reading. If speedometer displays a constant speed, go to next step. If speedometer fluctuates, see appropriate INSTRUMENT PANEL article in the ACCESSORIES/SAFETY EQUIPMENT section for speedometer diagnosis:
- Perform SPEED CONTROL SERVO test under TESTING. If servo is okay, go to next step. If servo is bad, replace servo.
- Turn ignition off. Disconnect Black 12-pin conventional instrument cluster connector or 16-pin electronic instrument panel connector. Disconnect amplifier connector. Measure resistance of Green/Yellow wire between cluster connector and amplifier connector. Measure resistance of Green/Yellow wire between cluster connector and ground. If resistance is less than 5 ohms between connectors, and more than 10,000 ohms between connector and ground, replace speed control amplifier. If resistances are not correct, repair Green/Yellow wire.