Symptom Related Diagnostic Procedures

1. Connect a Scan Tool to the ALDL Connector. Drive the vehicle. Observe the Speedometer and compare it to the vehicle speed shown on the Scan Tool.

^ If both the Speedometer and Scan Tool display the same approximate speed, check for correct tire size, ECM MEM-CAL and Vehicle Speed Sensor.

^ If the Scan Tool and Speedometer do not display the same approximate speed, replace or exchange the Instrument Cluster.

ALTERNATE TEST

^ If the Kent Moore Tool J38522 is available, do the following test.

2. Connect a Scan Tool to the ALDL connector. Disconnect the Vehicle Speed Sensor connector. Connect a lead between the J38522 vehicle speed generator's red output terminal and the Vehicle Speed Sensor connector terminal A (LT BLU). Connect a lead between the J38522 generator's black output and terminal B (DK GRN/YEL). Plug the generator into the Cigar Lighter. Select 30 V P-P sine wave and set the frequency at 600 hz. Observe the Speedometer and compare to the vehicle speed shown on the Scan Tool.

^ If both the Speedometer and Scan Tool display the same approximate speed, check for correct tire size, ECM MEM-CAL and Vehicle Speed Sensor.

^ If the Scan Tool and Speedometer do not display the same approximate speed, replace or exchange the Instrument Cluster.