P0505 Code: Idle Control System Malfunction
🟠 Moderate severity · drivable
Drivable, but the idle may surge or stall, so fix it soon for safe stop-and-go driving.
What P0505 means
The engine computer can't maintain the correct idle speed. The idle air control system — which lets a controlled amount of air bypass the throttle at idle — isn't responding correctly.
Symptoms
- Check engine light is on
- Rough or unstable idle
- Engine stalling at stops
- Surging idle speed
Common causes
- most common: Dirty or faulty idle air control (IAC) valve
- common: Vacuum leak
- common: Dirty throttle body
- less common: Faulty throttle position sensor
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Clean the idle air control valve and throttle body | Yes | $10–40 |
| Replace a faulty idle air control valve | Yes | $50–200 |
| Find and repair vacuum leaks | Yes | $10–100 |
Frequently asked questions
Can I drive with a P0505 code?
Yes, but the engine may stall at idle. Fix it soon, especially if you do a lot of city driving.
What is the most common cause of P0505?
A dirty or failing idle air control valve. Cleaning it often fixes the problem.
How much does it cost to fix a P0505?
Usually $10–$200. Cleaning is cheap; a new idle air control valve costs more.
Related codes
P0506
P0506 Code: Idle Air Control System RPM Lower Than Expected
P0507P0507 Code: Idle Air Control System RPM Higher Than Expected
P0110P0110 Code: Intake Air Temperature Sensor 1 Circuit
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.