Tachometer Is Inoperative Or Inaccurate (3.8L Not Using Instrument Panel Tester)

1. Disconnect instrument cluster connector. Start engine. Check voltage between ground and instrument cluster connector terminal D7 (White wire). See Figure . About 1.5 volts should be present at idle and voltage should increase with engine RPM.
2. If voltage is as specified, replace tachometer. If voltage is not as specified, check for open in White wire between instrument cluster and CCCI module. If White wire is okay, replace CCCI module.

Fig 1: Locating Tachometer Signal Filter

Courtesy of GENERAL MOTORS CORP.