P0508 Fault Code

Idle Air Control System Circuit Low

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

The P0508 fault code indicates an issue with the Idle Air Control (IAC) system circuit, specifically that the voltage is lower than expected. This code is triggered when the powertrain control module (PCM) detects a low voltage condition on the IAC circuit.

• The IAC valve helps regulate the engine's idle speed by controlling the amount of air that bypasses the throttle plate.
• A malfunction in this system can cause various performance issues, including poor idle quality and stalling.

What are the symptoms of the P0508 code?

Symptoms of the P0508 fault code may include:

• Rough or unstable engine idle.
• Engine stalling when the vehicle comes to a stop.
• Difficulty starting the engine.
• Decreased fuel efficiency due to improper air-fuel mixture.
• The check engine light illuminating on the dashboard.

What causes the P0508 code?

Common causes of the P0508 fault code include:

• A faulty IAC valve that may be stuck or malfunctioning.
• Open or short circuits in the IAC wiring or connectors.
• Issues with the PCM or a potential software glitch.
• Vacuum leaks affecting the intake manifold, resulting in incorrect idle air levels.
• Dirty or carboned-up throttle body restricting air flow.

How to fix P0508?

To resolve the P0508 fault code, the following steps may be necessary:

• Inspect the IAC valve and its electrical connectors for damage or corrosion.
• Test the IAC valve to ensure it operates correctly; replace if faulty.
• Check the wiring and connectors for shorts or opens; repair or replace as needed.
• Clean the throttle body to ensure proper air flow.
• Reset the codes and take the vehicle for a test drive to verify the issue is resolved.