P0505

Idle Air Control System Malfunction

OBD-II diagnostic trouble code P0505indicates a fault detected by the vehicle's onboard computer. This code applies to all OBD-II compliant vehicles and should be addressed promptly to avoid potential engine or emissions system damage.

Severity Level 3 — Moderate

This code indicates a moderate issue that may affect vehicle performance and fuel economy. Continued driving is possible in most cases, but prompt diagnosis and repair are recommended to prevent further damage.

Common Symptoms

• Check Engine Light on
• Engine idle speed too high or too low
• Engine stalling when coming to a stop or when AC compressor engages
• Surging idle — RPM fluctuates up and down at idle
• Hard starting — engine dies immediately unless giving throttle

Possible Causes

• Faulty IAC (idle air control) valve — carbon buildup jams the pintle, or solenoid fails electrically
• Carbon buildup in throttle body blocking the IAC air bypass passage
• Vacuum leak — allows unmetered air, IAC cannot compensate enough
• Damaged wiring or corroded connector at IAC valve
• Dirty throttle body not allowing throttle plate to close to proper idle position
• Faulty PCM (rare)

Common Fixes

• Clean IAC valve and throttle body of carbon deposits ($50-200 shop, $10-20 DIY with throttle body cleaner)
• Replace IAC valve ($60-250 parts, 10-minute DIY on most engines)
• Diagnose and repair vacuum leak ($100-250 diagnostic + $20-400 repair)
• Repair damaged wiring/connector at IAC valve ($30-150)
• Perform idle relearn procedure after cleaning/replacement ($0-100 diagnostic fee)

Estimated Repair Cost

These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.

Explore Repair Costs

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