Code P0506 - 2005 Ford Crown Victoria - low idle, stalling

Customer Complaint: Intermittent stalling Action Taken: Test drove the car and was able to reproduce the condition. Also noticed a low idle. Hooked up my Genisys Scan Tool and found a history code P0506. Checked Idle speed at 500 rpm, should be around 750 rpm P0506 : Idle Control System RPM Lower Than Expected Normally you would jump to the IAC ( Idle Air Control ) but this vehicle does not have one as it is Throttle by wire (electronic throttle control - ETC). Description: Vehicles with electronic throttle control (ETC) This DTC is set when the powertrain control module (PCM) detects an engine idle speed that is less than the desired RPM. Possible Causes: 1) Air intake restriction 2) Exhaust restriction 3) Engine mechanical fault. 4) Damaged electronic throttle body (ETB) 5) Damaged PCM 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 and damage. If no concerns are present, clear the DTC and retest. Solution: I found carbon build up in the Throttle Body at and around the butterfly inside the throttle body. Some brake wash and a rag quickly removed the carbon build up. Tested, and Idle speed was up from 500 rpm to 800 rpm. Test drove and the vehicle performed as it should. Fixed!!