Idle Control System Malfunction
The Idle Air Control (IAC) system is not maintaining proper engine idle speed. This code indicates the PCM detected an issue with the IAC motor or its circuits that control how much air bypasses the throttle valve at idle.
What You Might Notice
- Check Engine Light (MIL) illuminated
- Engine stalls or dies at idle
- Engine idle speed too high or too low
- Engine stalls when releasing throttle
- Engine requires throttle depression to stay running
Most Common Causes
- 1
IAC motor connector damage
The IAC connector pins may be corroded, loose, or damaged, or moisture may have entered the connector, preventing proper electrical communication.
- 2
Open or shorted IAC circuits
The wiring harness connecting the IAC motor to the PCM may have an open circuit, short to ground, or short to voltage, disrupting signal transmission.
- 3
IAC motor failure
The IAC motor itself may have failed or seized, preventing it from controlling idle air bypass properly.
- 4
PCM malfunction
The Powertrain Control Module may have failed or lost its ability to command the IAC motor correctly.
How to Diagnose It
- 1
Check IAC motor connector damage — The IAC connector pins may be corroded, loose, or damaged, or moisture may have entered the connector, preventing proper electrical communication.
- 2
Check Open or shorted IAC circuits — The wiring harness connecting the IAC motor to the PCM may have an open circuit, short to ground, or short to voltage, disrupting signal transmission.
- 3
Check IAC motor failure — The IAC motor itself may have failed or seized, preventing it from controlling idle air bypass properly.
- 4
Check PCM malfunction — The Powertrain Control Module may have failed or lost its ability to command the IAC motor correctly.
How to Fix It
- 1
Inspect and clean IAC connector
Remove the IAC connector and inspect all pins for corrosion, bending, or damage. Clean the connector with electrical contact cleaner and reinstall firmly. Ensure no moisture is present.
- 2
Test IAC wiring harness
Using a multimeter, test the IAC motor circuits for continuity and verify there are no shorts to ground or voltage. Repair or replace damaged wiring as needed.
- 3
Replace IAC motor
If wiring and connectors are sound, remove and replace the IAC motor with a new or rebuilt unit. Follow manufacturer specifications for installation and initial setup.
- 4
Test or replace PCM
If all IAC components test good, have the PCM tested for faults or reprogrammed. If defective, replacement may be necessary; consider professional diagnostic support.
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