Speedometer Is Inoperative Or Inaccurate (3.1L Engine)

1. If ECM Code 24 is set, proceed to SPEEDOMETER IS INACCURATE & ECM CODE 24 IS SET test under SPEEDOMETER/ODOMETER. If ECM Code 24 is not set, go to next step.
2. Raise and support vehicle. Disconnect Vehicle Speed Sensor (VSS) from top of transaxle. Connect Signal Generator Instrument Panel Tester (J-33431-B) to VSS connector. Set tester to 54 MPH. Turn ignition on. If speedometer does not reads 6 MPH, go to next step. If speedometer reads 6 MPH, check for poor connection at VSS. If connection is okay, replace VSS.
3. Turn ignition off. Disconnect tester from VSS. Disconnect VSS buffer located behind instrument panel, above convenience center. See Fig 1 . Connect Signal Generator Instrument Panel Tester (J-33431-B) to terminal "F" (Dark Green wire) of VSS buffer connector C1. See Fig 1 .
4. Set tester to 54 MPH. Turn ignition on. If speedometer reads 54 MPH, check for poor connection at VSS buffer. If connection is okay, replace VSS buffer. If speedometer does not read 54 MPH, check for open or short circuit in Dark Green wire or for poor connection at instrument cluster. If wire and connection are okay, replace speedometer.

Fig 1: Locating VSS Buffer (3.1L Engine)

Courtesy of GENERAL MOTORS CORP.