P0508 Idle Air Control System Circuit Low

Definition: The P0508 code indicates that the Engine Control Module (ECM) has detected a low voltage condition in the idle air control system circuit. This typically means there is an issue with the idle air control valve or its wiring, causing it to not function properly and affecting the engine’s ability to maintain a stable idle speed.

p0508 – Idle Air Control System Circuit Low

Typical severity: Moderate

Common Causes

p0508 – Idle Air Control System Circuit Low

Description: The PCM has detected an abnormally low voltage in the idle air control (IAC) system circuit.

Common Causes:

• Faulty idle air control valve
• Wiring issues such as short circuits or open circuits in the IAC circuit
• Poor electrical connection to the IAC valve
• PCM software needs to be updated

 

Common Misdiagnosis

OBD2 Code: P0508

Description: Idle Air Control System Circuit Low

Common Misdiagnosis: Replacing the idle air control valve without checking for wiring issues or vacuum leaks.

 

Common Diagnostic Steps

OBD2 Code: P0508

Description: Idle Air Control System Circuit Low

• Check for any stored trouble codes and freeze frame data to understand the conditions under which the code was set.
• Inspect the idle air control (IAC) valve and its wiring for damage, disconnections, or corrosion.
• Test the IAC valve resistance using a multimeter to ensure it is within manufacturer specifications.
• Verify that there are no vacuum leaks in the intake system that could affect idle speed control.
• Examine the throttle body for carbon buildup or obstructions that may impede airflow.
• Use a scan tool to monitor IAC operation and check if it responds correctly to commands from the engine control module (ECM).
• If applicable, update or reflash ECM software as per manufacturer recommendations.
• If all tests pass but the issue persists, consider replacing the IAC valve with a new one. Ensure compatibility with your vehicle model.