DTC P1509 - IAC SYSTEM HIGH RPM GMC Envoy I

Note. For circuit reference, see WIRING DIAGRAMS - 4.3L article.

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

1. No ECT, MAP, TP or VSS sensor DTCs set.
2. ECT greater than 161.6°F (72°C).
3. IAT greater than -13°F (-25°C).
4. BARO greater than 70 kPa (10,300 ft.).
5. Vehicle speed less than 2 MPH.
6. TP is less than one percent.
7. Engine running more than 30 seconds.
8. System voltage 10-16 volts.
9. Conditions met for greater than 3 seconds.
10. Change in calculated airflow greater than 2 counts.