Vehicle Speed Sensor (VSS)
Diagnostic Codes: P 0500Monitoring Procedure
An engine load test will check for a sustained high engine load being present within a given range of engine speeds and a low road speed. The tests will be different for manual and automatic transmission vehicles. Electronic automatic transmission vehicles have a test using the transmission retard request signal; if these requests are being made at a low road speed then the test will fail. No default strategy is applied to the road speed input. If these tests are not passed then a fault event has occurred.
When sufficient fault events have occurred then a fault is registered. The strategy will report to the Diagnostic Status Manager (DSM) when a VSS monitoring fault is present and the DSM will then decide whether to store a fault code and illuminate the MIL Lamp.
Possible Causes:
- Transmission CM fault - sends ignition retard requests whilst stationary
- Road speed sensor fault
- Road speed signal pulled down by another consumer ECM
- Road speed signal swamped by Radio Frequency Interference (RFI)
- Road speed signal wrongly sent by another ECM
- ECM load signal is wrong high - but undetected