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Code
P0509
Idle

Idle air control circuit high input

The idle air control circuit reads too high.

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Most likely causes

  1. Faulty IAC valve
  2. Open wiring
  3. Bad driver

Symptoms you may notice

  • High idle

Checks to run

  1. Test the valve
  2. Check wiring

Tools you may need

Multimeter
Always diagnose before replacing. Codes share symptoms; confirm the cause with measurements before buying parts.

Related codes in Idle

P0507

Idle speed higher than expected

 P0506

Idle speed lower than expected

 P0508

Idle air control circuit low input
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