Idle Air Control Valve Circuit Open (Chrysler)
What does P1508 mean?
The P1508 code means the vehicle's onboard diagnostic system has detected: Idle Air Control Valve Circuit Open (Chrysler). This is a moderate severity code.
Common Symptoms
- Engine stalls at idle
- Check Engine Light illuminated
- Idle speed drops very low or to zero
- Engine dies when foot is taken off the gas
- Rough or unstable idle
Probable Causes (Ranked by Likelihood)
- Failed IAC valve motor Very High
- Disconnected or broken wiring to the IAC valve High
- Corroded IAC valve connector High
- Damaged PCM output driver for IAC control Moderate
- Open circuit in the IAC valve harness Low
Step-by-Step Diagnostic Procedure
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Check the IAC valve connector for corrosion, loose pins, or a disconnected plug.
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Measure the IAC valve motor coil resistance. Typical values are 7 to 13 ohms per winding.
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Verify voltage at the IAC connector when the engine is running. The PCM pulses voltage to control the valve.
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Inspect the wiring harness from the PCM to the IAC valve for breaks or chafing.
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Command the IAC with a scan tool and observe if the idle speed changes.
Frequently Asked Questions
What does 'circuit open' mean?
An open circuit means there is a break in the electrical path between the PCM and the IAC valve. This could be a disconnected wire, corroded connector, or a burned-out motor coil inside the valve.
Can I test the IAC valve with a battery?
You can apply 12V briefly to each IAC motor terminal to see if the pintle extends or retracts. If there is no movement, the motor is likely failed internally.
Is this different from P1509?
Yes. P1508 indicates an open circuit (no electrical connection), while P1509 indicates a short circuit (unintended connection to ground or power). Both affect the same IAC valve but require different diagnostic approaches.