Dirty throttle body or idle air control passage; Faulty idle air control valve (older engines); Vacuum leak (high idle); Idle relearn needed after battery disconnection or throttle body cleaning; Faulty electronic throttle body.

P0505: Idle Air Control System

Q: What does P0505 mean?

P0505: Idle Air Control System. The engine computer cannot control idle speed as commanded.

Q: Is it safe to drive with P0505?

Severity: Moderate. Drivable with care. Diagnose soon: performance, economy or other components can be affected.

P0505 means Idle Air Control System. The engine computer cannot control idle speed as commanded.

CodeP0505

SystemIdle control

SeverityModerate

TypeGeneric powertrain

Can I keep driving? Drivable with care. Diagnose soon: performance, economy or other components can be affected.

Common symptoms

Check engine light on
Idle speed too high, too low or hunting
Stalling when coming to a stop
Rough idle

Possible causes

Dirty throttle body or idle air control passage
Faulty idle air control valve (older engines)
Vacuum leak (high idle)
Idle relearn needed after battery disconnection or throttle body cleaning
Faulty electronic throttle body

How to diagnose P0505

Clean the throttle body.
Check for vacuum leaks.
Perform the manufacturer's idle relearn procedure.
Check the idle air control valve or electronic throttle operation on a scan tool.

What the code means, digit by digit

PPowertrain0Generic (SAE) code5Sub-system05Specific fault

Generic codes have the same definition on every OBD-II vehicle (petrol cars from model year 1996 in the US, 2001 in the EU; diesels later). Manufacturers can add their own enhanced codes; those are not listed here.

Symptoms linked to P0505

Rough idle Car stalls at idle or when stopping

Related codes

General guidance only. Fault codes describe what the engine computer saw, not which part failed: confirm with testing before replacing parts, and follow the vehicle's service information.