Idle Air Control Valve Circuit Short (Chrysler)
What does P1509 mean?
The P1509 code means the vehicle's onboard diagnostic system has detected: Idle Air Control Valve Circuit Short (Chrysler). This is a moderate severity code.
Common Symptoms
- Idle speed too high or too low
- Check Engine Light illuminated
- Engine idles erratically
- IAC valve buzzes or chatters
- Engine may stall intermittently
Probable Causes (Ranked by Likelihood)
- Shorted wiring in the IAC valve circuit Very High
- IAC valve motor internally shorted High
- Water intrusion in the IAC connector High
- Chafed wiring touching the engine block or bracket Moderate
- PCM output driver damaged from short Low
Step-by-Step Diagnostic Procedure
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Inspect the IAC valve connector for moisture, corrosion, or pins shorted together.
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Measure IAC motor coil resistance. Low readings (under 5 ohms) indicate an internal short.
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Check the wiring from the PCM to the IAC for insulation damage where it contacts metal.
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Disconnect the IAC and check for short to ground on each wire with a multimeter.
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Replace the IAC valve if coil resistance is out of specification.
Frequently Asked Questions
Can a short circuit damage the PCM?
Yes. A prolonged short can overheat and damage the PCM output driver that controls the IAC valve. If the short is in the wiring, fix it before installing a new IAC valve to avoid damaging the PCM.
Why does the IAC valve buzz?
A shorted winding in the IAC motor or shorted wiring causes erratic current flow, making the valve vibrate or chatter instead of moving smoothly. This is a clear sign of a short circuit.
Should I replace the IAC valve and wiring at the same time?
If wiring damage caused the short, always repair the wiring first. Then test the old IAC valve resistance. If it is within specification, the wiring was the problem. If resistance is low, replace the valve too.