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). When PCM detects too high of an idle speed and is unable to adjust idle speed, DTC P0507 will set and MIL will be illuminated on second consecutive trip this is detected.

Conditions required to set DTC are:

• Engine run time is more than 125 seconds.
• No ECT, EGR, IAT, MAP, TP, VSS sensor, misfire, low voltage, fuel system or canister purge DTCs set.
• BARO is greater than 72.7 kPa.
• Canister purge duty cycle is greater than zero percent.
• ECT is greater than 122°F (50°C).
• IAT is more than -40° (-40°C).
• MAP is less than 60 kPa.
• Throttle is closed.
• Ignition voltage is 9.5-16 volts.
• Engine speed is at least 200 RPM less than desired idle.