hi guys i got wrx/sti import 1995 i got check engine light on i read code 22 knock sensor then i cleared code stayed off until car got warm came bk on again /why wud this do this and not wen warm/ wud the sensor need replacing

 

The ecu will only let the timing fully advance when the engine has warmed up. It is more than likely the sensor, i've known a few fail.

Plus it's the cheapest place to start.