DTC P0507: - Idle Air Control (IAC) System Rpm Higher Than Expected

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2009 Mercury Mountaineer, 2009 Mercury Milan, 2009 Mercury Mariner, 2009 Mercury Grand Marquis, and 2009 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0507: - IDLE AIR CONTROL (IAC) SYSTEM RPM HIGHER THAN EXPECTED

For Vehicles With an Idle Air Control (IAC) Valve
Description:	This DTC is set when the powertrain control module (PCM) detects an engine idle speed that is greater than the desired RPM.
Possible Causes:	IAC circuit shorted to ground Damaged or incorrect IAC valve IAC valve stuck open Intake air leak after throttle body Vacuum leaks Damaged EVAP system EGR valve leaks vacuum
Diagnostic Aids:	Disconnect the IAC valve and look for little or no change in engine RPM as an indication of a stuck or damaged valve.
For All others
Description:	This DTC is set when the powertrain control module (PCM) detects an engine idle speed that is greater than the desired RPM.
Possible Causes:	Intake air leak after throttle body Vacuum leaks Damaged EVAP system EGR valve leaks vacuum Damaged electronic throttle body (ETB) Damaged PCM
Diagnostic Aids:	This DTC is informational only and it may be accompanied by other DTCs. Diagnose other DTCs first. If other DTCs are not present inspect the intake air system for air or vacuum leaks and damage. If no concerns are present, clear the DTC and repeat the self-test.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
Ranger	GO to Pinpoint Test KE .
All others	Refer to the Description, Possible Causes and Diagnostic Aids for the DTC.