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P0505: Idle Air Control System Malfunction

What this check-engine code means in plain English, what usually causes it, and what a fix typically costs.

Severity: Monitor — not an emergency, but should be addressed soon

What P0505 means

This code means the engine control module (ECM) has detected that the idle air control (IAC) system is not maintaining the correct engine idle speed. The IAC valve regulates airflow into the engine when your foot is off the accelerator, and when it malfunctions, the computer cannot control idle speed properly.

What causes P0505?

Likely
Dirty or clogged IAC valveCarbon buildup restricts the valve's movement, preventing proper airflow control at idle.
Likely
Faulty IAC valveThe valve itself has failed electrically or mechanically and cannot respond to computer commands.
Possible
Vacuum leakUnmetered air entering the intake system bypasses the IAC valve, making idle control impossible.
Possible
Wiring or connector issuesDamaged wires or corroded connectors to the IAC valve prevent proper electrical signals.

Is P0505 safe to drive?

Drive it?
Usually yes, short-term
Watch for
Stalling, rough idle, or high/low idle speed
DIY-friendly?
Cleaning the IAC valve is DIY-friendly; replacement requires moderate skill.

You can typically continue driving with this code, but the engine may idle roughly, stall at stop lights, or have erratic idle speed. If the vehicle stalls frequently in traffic or won't stay running, address it promptly for safety.

P0505 repair cost

~$100 – $400+

Industry-average estimates. Cost depends on whether cleaning solves the problem or if valve replacement and additional diagnostics for vacuum leaks are needed.

Which one is it for your car?

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