P0502 — Vehicle Speed Sensor A Circuit Low
The primary vehicle speed sensor (VSS A) reports a signal voltage below the plausible lower limit. With no usable speed signal the ECU loses cruise control, gear-shift logic and certain anti-stall functions.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Vehicle speed sensor a
- Vss wiring
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Signal shorted to ground
- Sensor internal short
- Connector pins corroded - high contact resistance
Diagnostic notes
- The malfunction indicator lamp may illuminate
Related codes
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.