Check Engine Code
P0505
Idle Air Control System Malfunction
Severity: medium
DIY difficulty: 2/5
Typical cost: $15–$250
What P0505 means
Older (non-drive-by-wire) cars use an idle air control (IAC) valve to let a metered amount of air bypass the throttle plate at idle. P0505 means the ECM and the IAC aren't agreeing.
Symptoms
- Check engine light
- High or low idle
- Stalling at stops
- Surging at idle
Likely causes (most common first)
- Carbon buildup in the IAC valve (cleaning often fixes it)
- Failed IAC motor
- Vacuum leak masking as an IAC problem
- Dirty throttle body
- Wiring fault
Can I keep driving?
Medium — drivable but fix soon
Typical repair cost
DIY fixes can start near $15 (parts only). Shop repairs for P0505 typically run up to $250 depending on the underlying cause and vehicle. Start with the most common cause — Carbon buildup in the IAC valve (cleaning often fixes it) — before throwing parts at it.
Related codes
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