DTC P0506: Idle Air Control (IAC) System Rpm Lower Than Expected

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2011 Mercury Milan, 2011 Mercury Mariner, 2011 Mercury Grand Marquis, 2011 Lincoln Town Car, and 2011 Lincoln Navigator L. However, it is still accessible from the selected car via links, so may be relevant.

P0506 - IDLE AIR CONTROL (IAC) SYSTEM RPM LOWER THAN EXPECTED

For Vehicles With An Idle Air Control (IAC) Valve
Description:	This DTC sets when the powertrain control module (PCM) detects an engine idle speed that is less than the desired RPM.
Possible Causes:	IAC circuit open Air inlet is plugged B+ or VPWR to IAC solenoid open Damaged or incorrect IAC valve IAC valve stuck closed VPWR to IAC solenoid open IAC circuit short to voltage
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 sets when the powertrain control module (PCM) detects an engine idle speed that is less than the desired RPM.
Possible Causes:	Intake air restriction Vacuum leaks Exhaust restriction Engine mechanical concern Sludged throttle body Damaged electronic throttle body (ETB) Damaged PCM
Diagnostic Aids:	This DTC may be accompanied by other DTCs. Diagnose other DTCs first. If no other DTCs are present, inspect the intake air system for air restrictions, vacuum leaks, and damage. If no concerns are present, clear the DTC and carry out the key ON engine running (KOER) self-test.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
Ranger	GO to PINPOINT TEST KE .
All others	GO to PINPOINT TEST HU .