Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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 pulsing voltage to MPH, and MPH can be displayed using a Tech 1.
The function of 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 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 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).
- VSS signal generator only produces a signal if drive wheels are turning greater than 3 MPH.
- Check PROM for correct application before replacing PCM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.