Circuit Description

PCM controls idle speed with an Idle Air Control (IAC) valve to a calculated RPM based on sensor inputs and actual engine RPM. PCM moves IAC valve in or out to vary amount of airflow into intake manifold and thus decrease or increase idle RPM. PCM commands IAC in counts. A higher count, allows more air to by-pass throttle plate (higher idle).

DTC will set when engine speed is over 100 RPM less than desired idle. DTC will also set when, there is no fuel injector faults, misfire, fuel trim, CKP, ECT, EVAP, EGR, VSS, TP, IAT, MAP or MAF sensor DTCs set, BARO is greater than 65 kPa, engine running for at least 3 minutes, system voltage 9-18 volts, ECT greater than 158°F (70°F), vehicle speed is less than 3 MPH, IAT is greater than 0°F (-18°C) or when throttle is closed.