P0502 Fault Code

Vehicle Speed Sensor Circuit Low Input

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0502 code is triggered when the vehicle's Engine Control Module (ECM) detects a lower-than-expected voltage from the Vehicle Speed Sensor (VSS). This often indicates a malfunction in the VSS circuit, leading to improper readings of vehicle speed. The VSS plays a critical role in providing accurate speed data for various systems within the vehicle, including automatic transmission shifting and traction control.

What are the symptoms of the P0502 code?

Common symptoms that may arise when the P0502 code is present:

• Inaccurate speed readings on the speedometer.
• Erratic shifting behavior in automatic transmissions.
• Activation of the check engine light or warning indicators on the dashboard.
• Poor fuel economy due to incorrect speed-related calculations.

What causes the P0502 code?

Several factors can contribute to this issue including:

• A faulty Vehicle Speed Sensor itself.
• Damaged wiring or connectors in the speed sensor circuit.
• Poor electrical connections, leading to voltage drops.
• Issues with the ECM or its programming that affects sensor input interpretation.

How to fix P0502?

To resolve the P0502 code effectively, consider the following steps:

• Inspect the Vehicle Speed Sensor and its connections for any physical damage, corrosion, or looseness.
• Test the VSS to ensure it is functioning correctly; replace it if necessary.
• Check for any wiring issues or short circuits in the speed sensor circuit.
• Clear the fault code after repairs and take the vehicle for a test drive to verify that the issue is resolved.