Code Definition

P0502 — Vehicle Speed Sensor Signal Low - Sensor 1

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0502

P0502 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0502 is stored, the module has detected a signal or supply voltage lower than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0502 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The DTC P0502 is set when the Engine Control Module (ECM) or Transmission Control Module (TCM) detects a low signal voltage from Vehicle Speed Sensor 'A.' This low signal condition can result in inaccurate or non-functioning speedometer readings, improper transmission shift points, and can affect other systems that rely on vehicle speed data such as ABS and traction control. It typically points to a weakening or insufficient signal rather than a complete loss of signal.

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