Code 24, Vehicle Speed Sensor Circuit: Notes

ECM supplies a B+ signal to Vehicle Speed Sensor (VSS). While vehicle is moving, a reed switch inside VSS will open and close, toggling B+ signal high and low. ECM then converts this toggled high/low voltage into a vehicle speed that is displayed as MPH/KPH.

Code 24 will set if a constant voltage signal (high or low) is not detected at ECM for at least 4 seconds, with engine running and vehicle moving.

1. Checks if problem is intermittent.
2. If VSS is not receiving 12 volts from ECM, Code 24 will set. Checks for open in Yellow/Green wire or a faulty ECM.
3. Checks for a poor ground connection, an open in Black/Blue wire or a faulty VSS.