OBD
P0509
Idle Air Control System Circuit High
What it means
P0509 means Idle Air Control System Circuit High.
Check these first
- A short to power in the idle air control circuit
- A failed idle air control valve
- A chafed idle air control wire
- A faulty PCM driver
What to do next
- Check the idle air control circuit for a short to power
- Measure the idle air control valve resistance
- Inspect the idle air control wire for chafing
- Replace the idle air control valve if the circuit is shorted to power
- Clear the code and retest
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Updated
Generic SAE J2012 definition. Last updated 2026-10-10.