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.

Real-world scan data

Seen in

1,190

scans in the past year

Found in

0.2%

of scans

0.3%

of scans that found faults

Appears alongside · share of P0505 scans

P0123in 15.0% of scans

P0500in 12.9% of scans

P0113in 12.2% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P0505 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX