P0509
Idle Air Control System Circuit High
Generic code
Vehicle Speed and Idle Control System
High severity
Moderate repair
Free on OBD DashX
Want real-world data on P0509?
See which problems come with P0509, how often it shows up in other vehicles, and how to fix it — step by step.
- Real-world fix data
- How often it happens
- Step-by-step repairs
What P0509 means
- The fault code P0509 indicates that the engine control module (ECM) has detected a high voltage input from the idle air control (IAC) system circuit. This may cause the engine to idle too high or too low, or stall.
Possible symptoms
- Engine idles too high or too low
- Engine stalls at idle
- Illuminated check engine light
- Rough idling
- Poor fuel economy
Possible causes
- Faulty idle air control valve
- Failed engine control module (ECM)
- Wiring or electrical connections in the circuit are damaged, corroded, or loose
- Failure of the throttle body
Related parts
- Idle Air Control System: IAC (Idle Air Control) System controls the speed of the engine when it is idling. This car's engine may keep stalling due to problems with the IAC
Possible solutions
- Replace the idle air control valve
- Check and repair any damaged or corroded wiring or electrical connections in the circuit
- Replace the engine control module (ECM) if necessary
- Replace the throttle body
Free on OBD DashX
P0509 on OBD DashX
Real-world causes, how often this code shows up, and the fix — step by step.
Open P0509 No sign-up needed · available in 10 languagesScan your own car
Read and clear fault codes, live data and service resets with the CaRPM app.