OBD codes / P0505
P0505
ModerateIdle Air Control System Malfunction
P0505 is usually drivable, but stalling at stops can be inconvenient and occasionally catch you off guard. It's low-risk mechanically. Try cleaning the IAC valve and throttle body (with an idle relearn) before replacing parts — it fixes many cases cheaply.
What this code means
The idle air control (IAC) system meters a small amount of air past the throttle to keep a smooth idle when your foot is off the gas. P0505 is a general fault in that system — the computer can't hold the idle where it wants. The most common cause is a carbon-clogged IAC valve or a dirty throttle body restricting that airflow; a vacuum leak or IAC wiring fault can also cause it. Cleaning the IAC valve and throttle body resolves a lot of these, often followed by an idle relearn.
Symptoms you might notice
- Rough, unstable, or hunting idle
- Stalling at stops or when coming to a stop
- Idle that surges up and down
- Idle that dips when accessories switch on
- Check-engine light
What it costs to fix
Typical range: $50–$450 · about ~0.3–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| IAC valve / throttle body cleaning | $8–$20 | ~0.3–1 hrs |
| Idle air control (IAC) valve | $30–$150 | ~0.3–1 hrs |
| Vacuum / intake leak repair | $10–$150 | ~0.5–2 hrs |
Cleaning is the cheap first step and frequently enough (do an idle relearn afterward). A replacement IAC valve is modest. A vacuum leak's cost depends on which hose or gasket leaks.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0505 for my exact vehicle →
Frequently asked
Can I drive with P0505?
Usually yes — a rough or stalling idle is annoying more than dangerous, though be ready for the engine to dip at stops. You can drive to get it cleaned or diagnosed.
Will cleaning fix P0505?
Often — carbon clogging the IAC valve or throttle body is the most common cause. Clean both and perform an idle relearn so the computer recalibrates. If it returns, the IAC valve may need replacing or there's a vacuum leak.
What's the difference between P0505, P0506, and P0507?
P0505 is a general idle-control fault; P0506 is idle too low; P0507 is idle too high. They overlap in causes (cleaning, IAC valve, vacuum leaks) but the high/low versions point you toward the direction of the problem.
How much does it cost to fix P0505?
Often cheap — cleaner and labor, plus an idle relearn. An IAC valve is modest; a vacuum-leak repair varies by location. Clean first before buying parts.
Seeing P0505 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0505 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.