P0502 Vehicle Speed Sensor Circuit Low Input

OBD-II Code: P0502

Description: Vehicle Speed Sensor Circuit Low Input

Definition: The P0502 code indicates that the vehicle’s Powertrain Control Module (PCM) has detected a low input signal from the vehicle speed sensor. This sensor is responsible for monitoring the speed of the vehicle and sending this information to various systems within the car, including the transmission and ABS.

p0502 – Vehicle Speed Sensor Circuit Low Input

Typical Severity: Moderate

Common Causes

p0502 – Vehicle Speed Sensor Circuit Low Input

Description: The vehicle’s ECM has detected a low input signal from the vehicle speed sensor.

Common Causes:

• Faulty vehicle speed sensor
• Wiring issues such as frayed or broken wires
• Poor electrical connection at the speed sensor
• Corrosion in the sensor connector
• Defective ECM (Engine Control Module)

Common Misdiagnosis

OBD2 Code: P0502

Description: Vehicle Speed Sensor Circuit Low Input

Common Misdiagnosis: Replacing the vehicle speed sensor without checking for wiring issues or connector problems.

Common Diagnostic Steps

OBD2 Code: P0502

Description: Vehicle Speed Sensor Circuit Low Input

Common Diagnostic Steps:

• Verify the code using an OBD-II scanner and clear it to see if it returns.
• Inspect the vehicle speed sensor (VSS) for any visible damage or corrosion.
• Check the wiring and connectors leading to and from the VSS for any signs of wear, damage, or disconnection.
• Test the VSS using a multimeter to ensure it is functioning correctly. Refer to the vehicle’s service manual for specific resistance values.
• Examine related fuses and replace them if necessary.
• If equipped, inspect the ABS wheel speed sensors as they can sometimes affect vehicle speed readings.
• If all components appear functional, consider testing or replacing the engine control module (ECM) as a last resort.