Code 24 - Vehicle Speed Sensor (VSS)
The ECM applies and monitors 12 volts on circuit 437. Circuit 437 connects to Vehicle Speed Sensor (VSS) which alternately grounds circuit when drive wheels are turning. This pulsing action takes place 2000 times per mile. The ECM calculates vehicle speed based on the time between "pulses".
NOTE:
The following step numbers refer to the step numbers in the accompanying Flow Chart.
- This test monitors the ECM voltage on circuit 437. With wheels turning, the pulsating action will result in a varying voltage. The variation will be greater at low speeds to an average of 4-6 volts at about 20 MPH.
- A voltage of less than 1 volt at ECM connector indicates that circuit 437 is shorted to ground. Disconnect 437 at VSS. If voltage now reads above 10 volts, the VSS is faulty. If voltage remains less than 10 volts, circuit 437 is grounded. If circuit 437 is not grounded, check for faulty ECM connector or ECM.
- A steady 8-12 volts at ECM connector indicates circuit 437 is open or a faulty VSS.
- This normal voltage condition indicates a possible intermittent problem. See the CCC TESTS W/O CODES article in this section.