Speedometer Head: Testing and Inspection

Symptom Table:

If your symptom is not listed in the symptom table, perform all the tests.

Test A:

TEST B:

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 speed, check for correct tire size, ECM CALPAK, and VSS drive gears. If OK, replace vehicle speed sensor.
^ If scan tool and speedometer do not display the same speed, replace the instrument cluster.