High idle - error showing on ECU

[Brown Dog]

Friday was driving home, been driving for perhaps 30mins, and stopped at lights. Car idled at about 1500 RPM, then gradually settled to ~1000
So i fired up my ODB app and it shows an error P0507 Idle Air Control System RPM higher than expected.
Today, idle again was high - maybe 900. Resulting in engine light coming on.
A few short trips later, light is off. Idle normal for now.

My phone has saved the error if I need to speak to a dealer
Weird eh.

 

[Brown Dog]

so what might cause this? no obvious loose hoses

 

[krusing]

Air intake error,
Dodgy fuel,
Sticking injector,
Sticking Throttle butterfly ,
Throttle Peddle sticking, resistance error being drive by wire,
Vacuum leak, where if it was a serious leak, it would of idled longer, but never the less, never assume,
Where do you start.

 

[SSteve]

This happened once to me. (Approx 12 months ago) Just like you explained above. Has never happened since