DTC P0505: Idle Air Control (IAC) System Malfunction

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2005 Mercury Sable, 2005 Mercury Mountaineer, 2005 Mercury Monterey, 2005 Mercury Montego, and 2005 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.

P0505 - IDLE AIR CONTROL (IAC) SYSTEM MALFUNCTION

For Vehicles With Electronic Throttle Control (ETC)
Description:	The powertrain control module (PCM) attempts to control engine speed during the key on, engine running (KOER) self-test. The test fails when the desired RPM could not be reached or controlled during the self-test.
Possible Causes:	Failure mode effects management (FMEM) condition is present Air inlet is plugged Vacuum leaks 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 restrictions, vacuum leaks, and damage. If no concerns are present, clear the DTC and retest.
For All Others
Description:	The powertrain control module (PCM) attempts to control engine speed during the key on, engine running (KOER) self-test. The test fails when the desired RPM could not be reached or controlled during the self-test.
Possible Causes:	IAC circuit open VPWR to IAC solenoid open B+ or VPWR to IAC solenoid open Air inlet is plugged IAC circuit shorted to PWR Damaged IAC valve
Diagnostic Aids:	The IAC solenoid resistance is 6 to 13 ohms. Monitor the IAC PID duty cycle and/or voltage.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
Vehicles With Electronic Throttle Control (ETC)	Refer to the Description, Possible Causes and Diagnostic Aids for the DTC.
All others	GO to KE: Idle Air Control (IAC) Valve STEP KE1.