Causes and Fixes P0505 Code: Idle Control System

How to fix a P0505 engine code: Idle Control System.
A P0505 code is set when the computer detects the engine RPMs at Idle are erratic.
An Idle Air Control (IAC) valve is controlled by the computer and allows air to bypass the throttle body butterfly.
Some newer vehicles can use an electronic Throttle Actuator System (ETC), which controls the throttle plate butterfly.
After cleaning or replacing throttle body parts, the engine may need an Idle Relearn Procedure.

Possible Causes of a P0505 Code
Dirty Throttle Body
Faulty Idle Air Control Valve (IAC)
Wiring
Vacuum leak

The information in this video is based on the OBDII protocol definitions, manuals, and my own experience. Always pay attention to any other DTC codes as they may point to a different cause.
If you have fixed this code and have information not provided let us know in the comments.
By using this information user assumes all risk of use.
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