The Vehicle Speed Sensor (VSS) generates a waveform with a frequency according to the speed of the vehicle. The signal generated by the VSS informs the ECM not only if the vehicle speed is low or high but also is stopped the vehicle or not. The ECM uses this signal to control the fuel injection, ignition timing, transmission/transaxle shift scheduling and torque converter clutch scheduling.
The ECM evaluates engine speed and mass air flow if there is no vehicle speed signal. This evaluation of both value will detect open circuit or short circuit error on vehicle speed sensor. The ECM sets DTC P0501 if there is no vehicle speed signal while both engine speed and mass air flow are higher than predetermined threshold during predetermined time.
If the same error code is set for 3 driving cycle, the ECM illuminates the MIL.
Item
Detecting Condition
Possible Cause
Case1
DTC Strategy
? Signal Check
? Contact resistance in connections.
? Open or Short in power circuit
? Open or Short in signal circuit
? Open in ground circuit
? Faulty VSS
? Faulty ECM
Enable Conditions
? Engine Load > 50 %
? Engine speed > 3000 rpm
? Coolant Temperature > 65?
Threshold Value
? No signal(during injection) < 3.75 km/h
Case2
? Engine coolant temperature > 65 C
? 1520 rpm < Engine speed < 4000 rpm
? No signal (during fuel cut-off) < 10 km/h
Diagnostic Time
? 20 sec
MIL ON Condition
? 3 Driving Cycle