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)

  1. Carbon buildup in the IAC valve (cleaning often fixes it)
  2. Failed IAC motor
  3. Vacuum leak masking as an IAC problem
  4. Dirty throttle body
  5. 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

P0506P0507

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