Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
VCM controls idle speed with an Idle Air Control (IAC) valve to a calculated RPM based on sensor inputs and actual engine RPM. VCM moves IAC valve in or out to vary amount of airflow into intake manifold and thus decrease or increase idle RPM.
VCM commands IAC in counts. A higher count, allows more air to by-pass throttle plate (higher idle).
Conditions for setting DTC:
- No ECT, MAP, TP or VSS sensor DTCs set.
- ECT greater than 122°F (50°C).
- IAT greater than -13°F (-25°C).
- BARO greater than 10.2 psi (0.72 kg/cm2 ) at 10,300 ft.
- Vehicle speed less than 2 MPH.
- Throttle angle at less than 1 percent.
- Engine running greater than 30 seconds.
- Conditions met for greater than 3 seconds.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.