P0505 — Idle Control System
Moderate severityWhat it means
P0505 is stored when the engine control unit sees a fault involving the idle air control system. The idle control system regulates engine speed at idle by metering air around or through the throttle. The control unit has flagged this circuit or signal as outside its normal operating range.
Common symptoms
- Idle too high, too low, or hunting
- Stalling at stops
- Slow return to idle
Likely causes
- A wiring, connector or ground problem in the circuit
- A failed sensor or actuator in the circuit
- Carbon buildup in the throttle body or idle passage
- Faulty idle-air control valve
What to check first
- Inspect the connector and wiring for damage, corrosion or loose pins
- Clean the throttle body and idle passages
- Check for vacuum leaks and perform an idle relearn
Can you keep driving?
Usually drivable, but stalling at junctions is a safety concern — fix it soon.
Scan, log and diagnose with MechanicAI
Plug a Bluetooth OBD2 adapter into your car and let MechanicAI turn raw data into answers:
- Scan, read and clear fault codes in seconds
- Inspect every sensor with live data
- Create instant logs and automatic trip records
- And above all — analyze it all with AI for the most likely cause and clear next steps.
Related codes
All information, explanations and guidance on this page are general preliminary information only. They are estimates and may be entirely wrong, incomplete or inaccurate, or may not apply to your vehicle at all. Never take any action based on this content alone — do not decide to keep driving, clear codes, replace parts, repair or otherwise work on your vehicle based only on what you read here. In every case, and for any final decision, you must consult qualified technical personnel (a professional mechanic, an authorized service centre or an engineer) and obtain their approval before acting. MechanicAI accepts no liability or responsibility whatsoever for any damage, fault, injury, loss or outcome that may arise — directly or indirectly — from using or relying on this information, for any reason and under any circumstances. By using this page you acknowledge and accept these terms.