Vehicle Application: 2003 Silverado 2500 HD 6.0
Customer Concern: Tachometer does not work right all the time, same with the speedometer.
Tests/Procedures: 1. Check the other gauges. If they also do not work right, check the data line and power/ground to the cluster.
2. If the other gauges are OK and the scanner shows good speed and RPM readings send the cluster out for testing.