Codes P0501/P0502, VSS Circuit: Notes

The Vehicle Speed Sensor (VSS) in transaxle provides vehicle speed information to PCM. Voltage level and number of pulses increase with vehicle speed. PCM converts the pulsing voltage to MPH, and the MPH can be displayed using a Tech 1.

The function of the VSS buffer, used in past models, has been incorporated into PCM. PCM supplies necessary signal for instrument cluster (4004 pulses per mile) for operating speedometer and odometer.

Code P0501 will set when the following conditions are present.

Engine is running.
Code P0703 is not set.
Transmission is out of Park or Neutral for more than 4 seconds.
Vehicle speed is greater than 18 MPH.
Brake is not applied.
All conditions are met for 2 seconds.

Code P0502 will set when the following conditions are present.

Vehicle speed goes from less than 3 to zero MPH in less than 2 seconds, brake not applied.
Engine is running.
Engine speed is greater than 3000 RPM.
Transmission is out of Park or Neutral for more than 4 seconds.

With Codes P0501 or P0502 set, cruise control operation will not be allowed. Code will remain set for remainder of that ignition cycle, and PCM will command only 2nd and 3rd gear based on RPM and TP sensor. TCC will not be allowed to engage. Instrument cluster speedometer may be inoperative. Codes P0501 and P0502 will illuminate Malfunction Indicator Light (MIL).

NOTE: Test numbers refer to numbers on diagnostic chart.

VSS signal generator only produces a signal if drive wheels are turning greater than 3 MPH.
Check PROM for correct application before replacing PCM.