P0505
Idle Control System
Idle control
Generic OBD-II
High
What it means
P0505 means the ECM can't keep the engine's idle speed within its expected range using the idle air control valve or electronic throttle. It usually points to a dirty throttle body, a sticking IAC valve, or a vacuum leak, and it shows up as an unstable idle or stalling at stops.
High
Can I keep driving? Drivable, but the engine may idle erratically or stall at stops until the idle-control fault is fixed — which can be hazardous in traffic.
Common symptoms
What you'll notice
- Check-engine light on
- Idle speed too high, too low, or hunting up and down
- Stalling when coming to a stop or when cold
- Rough idle, especially with the A/C or other loads on
Common causes
Most likely first
- Dirty or clogged throttle body and idle air passages (most common)Likely
- Sticking or failed idle air control (IAC) valve, where fittedCommon
- Vacuum leak in the intake manifold or hosesCommon
- Wiring or connector fault at the IAC valve or throttle bodyLess often
- Faulty ECM (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame and watch idle speed and the idle-control command live to see how the idle is drifting.
- Clean the throttle body and idle air passages; on drive-by-wire cars perform any required throttle relearn afterward.
- Test or clean the IAC valve if the vehicle has one, and check its wiring and connector.
- Smoke-test the intake for vacuum leaks that force the idle control out of range.
- Clear the code and confirm idle stabilises through a cold start and warm idle.
FAQ
Quick answers
Is it safe to drive with P0505?+
You can drive, but unexpected stalling at stops is a real risk, so treat it as a soon-to-fix item rather than ignoring it.
Can I just clear P0505?+
Clearing helps only briefly. Unless the throttle body, IAC valve or vacuum leak is addressed, the erratic idle and code return.
Related codes
Often seen with P0505
Read & clear P0505 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX