P0505 OBD-II code — what it means and what to check

ℹ Guidance only — not a substitute for inspection

Enter the trouble codes from your scanner to see what each one means, how urgent it is, and which checks to do first.

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Your trouble codes

Enter the codes exactly as your scanner shows them. Separate several codes with spaces or commas.

A letter followed by four characters, for example P0301. Up to ten codes at a time.
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Your codes, interpreted

What this means
⚠ Book a service. The codes you entered describe faults that get worse, or more expensive, if left.
What to doBook a workshop inspection. Normal driving is usual with these faults, but they should not be left indefinitely.

Your codes

  1. P0505 — Engine control (service soon). The engine cannot hold its target idle speed. The computer is having to correct further than it should, usually because unmeasured air is getting in.

Checks to do first, in order

  1. Inspect the intake hoses, the PCV system and the manifold gasket for vacuum leaks — the most common cause by a clear margin.
  2. Check the throttle body for carbon build-up around the plate.
  3. Check the idle air control valve for sticking, on engines that have one.
  4. If the battery was recently disconnected, have the idle relearn procedure carried out before chasing anything else.

Codes this tool cannot interpret

How this result was reached
  • Interpretations cover standardised codes only, and describe what a code means rather than what is wrong with your specific vehicle.
  • A stored code identifies the circuit or system reporting a fault. It does not identify the failed part — a sensor commonly reports a problem it did not cause.
  • Reviewed by Project Owner on 2026-08-26.
  • This tool covers a reviewed subset of standardised codes. A code it does not recognise is reported as undocumented rather than guessed at.