DTC P0506: Idle Control System Rpm Lower Than Expected - IMPREZA & Legacy 2.2L (CALIFORNIA Emissions)

Turn ignition off. Connect scan tool. Turn ignition on. Retrieve DTCs. If DTC P0505 exists, diagnose DTC P0505. Do not diagnose this DTC. If DTC P0506 is only DTC set, go to next step.
Turn ignition off. Remove IAC solenoid valve from throttle body. Using an air gun, force air into IAC solenoid valve installation area. Ensure air escapes from installation area. If air escapes, go to step 4. If air does not escape, replace IAC solenoid valve, then go to next step.
Start and warm engine. Observe IAC solenoid valve duty ratio. If value is more than 60 percent, go to next step. If value is 60 percent or less, test is complete.
Turn ignition off. Remove IAC solenoid valve. Remove throttle body. Ensure no foreign materials are stuck in air by-pass line. Using air gun, force air into IAC solenoid valve installation area and throttle valve interior. If air escapes from both these areas, replace IAC solenoid valve. If air does not escape, replace throttle body.