DTC 21 - Vehicle Speed Sensor (VSS) Open Or Shorted: Notes

The VSS is an electronic relay mounted on the transaxle. As the axles turn VSS sends voltage pulses (speed input) to the speedometer. The speedometer then converts speed input to a more precise waveform and sends this signal to the CCM. The CCM converts this signal into a vehicle speed. The speedometer also sends a signal to the Engine Control Module (ECM) and Powertrain Control Module (PCM).

1. This determines if VSS is functioning normally.
2. Checks for open in power feed to VSS.
3. Checks for open or short in CCM Speed input circuit or for a faulty CCM.
4. This determines if the CCM or speedometer is faulty.
5. Checks for open in ground to VSS.
6. Checks for open in power feed to speedometer.
7. This determines if the VSS or speedometer is faulty.