P0505
P0505 Idle Air Control System
P0505 is a generic OBD2 powertrain diagnostic trouble code for idle air control system. The code identifies the system or circuit the engine computer flagged, but diagnosis still depends on vehicle symptoms, freeze-frame data, and related codes.
How urgent is P0505?
Idle-control faults can make the car hard to control at stops and often point to air leaks or throttle-body issues.
Common symptoms
- High idle
- Low idle
- Surging idle
- Stalling
- Check engine light
Likely causes
- Vacuum leak
- Dirty throttle body
- Idle air control fault
- PCV leak
- Throttle relearn needed
What to check before replacing parts
1
Inspect for vacuum leaks
2
Check throttle body condition
3
Review desired vs actual idle RPM
4
Inspect PCV hoses
5
Perform idle relearn when required
Use the code with symptoms
A code points at the system, not always the failed part. Add your vehicle, mileage, symptoms, and whether the check engine light is steady or flashing so the AI diagnostic can narrow the next step.