C0100

CIRCUIT DESCRIPTION
Vehicle speed information is provided to the Power Steering Control Module (PSCM) by the Powertrain Control Module (PCM) and the class 2 data line. Once vehicle speed has been detected, the PSCM compares the vehicle speed signal received from the VSS with the vehicle speed data received from the class 2 data line. The VSS is a permanent magnet sensor producing an AC signal with varying frequency. The VSS is mounted in the transmission or transfer case (4x4 models) and is driven off the output shaft. The VSS produces a pulsing AC voltage when vehicle speed is greater than 5 km/h (3mph). The AC voltage and the number of pulses increase with vehicle speed. The VCM supplies the vehicle speed signal to the Instrument Cluster and to the PSCM.

CONDITIONS FOR SETTING THE DTC
1. When there is a difference of more than 10 km/h (6 mph) between the class 2 vehicle speed message for 10 seconds and the vehicle speed sensor is less than 5 km/h (3 mph).
2. The above conditions have been met for 5 consecutive class 2 samples.

ACTION TAKEN WHEN THE DTC SETS
The PSCM will not send any current to the power steering fluid flow actuator. This will result in the power steering fluid flow actuator valve to retract providing maximum fluid flow and full power steering assist at all times.

CONDITIONS FOR CLEARING THE DTC
1. A history DTC will clear after 100 consecutive ignition cycles has occurred without a fault.
2. History and current DTC(s) can be cleared by using the Tech 2 scan tool.

DIAGNOSTIC AIDS
- If a DTC P0500 or any other vehicle speed related codes are set perform those table first.
- A scan tool will show vehicle speed when the drive wheels are turning faster than 5 km/h (3 mph). The vehicle speed display should not be used if the drive wheels are not turning.
- An "Intermittent" problem may be caused by a poor connection, break in the wire insulation exposing the internal wire, or a wire that is broken inside the insulation.
- The Power Steering Control Module (PSCM) and the Vehicle Control Module (VCM) or Powertrain Control Module (PCM) should be thoroughly checked for terminals that have backed out, broken locks, improperly formed or damaged terminals, weak terminal retaining tension, or for proper routing.

TEST DESCRIPTION
The step numbers below refer to the same step numbers in the Vehicle Speed Information Circuit Malfunction Diagnostic Table.
- Step 1 ensures that the "Diagnostic System Check" has been performed.
- Step 2 checks the vehicle speed signal to the PCM.
- Step 3 makes sure other systems on the same circuit are receiving a VSS signal.