Code 24, Vehicle Speed Sensor Circuit: Notes

ECM supplies 12 volts to VSS. With vehicle moving, the reed switch inside the VSS will open and close 4 times per revolution of speedometer cable. As the reed switch opens and closes, voltage at the ECM is toggled high and low. ECM converts this toggled voltage into vehicle speed displayed as MPH or KPH. Code 24 will set if a constant voltage (high or low) lasts at least 4 seconds.

1. Checks for intermittents.
2. Checks for VSS not receiving 12 volts from ECM (open in Yellow/Green wire or faulty ECM).
3. Checks for poor ground connection or a faulty VSS.