OBD-II code · Powertrain (generic)
P0505 Idle Air Control System Malfunction
A general fault has been detected in the idle air control (IAC) system. On older vehicles with a separate IAC valve, this means the valve cannot maintain commanded idle RPM; on drive-by-wire systems, the equivalent fault is in the throttle body's idle adaptation.
Is it safe to drive with P0505?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyIAC valve carboned, sticky
- PossibleThrottle body dirty (drive-by-wire)
- PossibleVacuum leak affecting idle
Symptoms
- Check engine light on
- Idle speed too high, too low, or unstable
- Possible stalling at idle or after cold start
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–2.5 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Idle Air Control Valve, Throttle Body
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.