My 2000 alero with a 2.4 atou.tranmission has started to idle very high. Cold start it runs at upward to 3500rpm. When it warms up it gose down to 1200 rpms. Under load in sits at 1100 rpms.

trans..maybe, when you start it cold, and let it idle, (even high) will it eventually come down, even 200 rpm?

Once its warm it should be around 600-750 rpm. Does it sound like its idling high or is that what the gauge says? What is a high idle motor, are you referring to the idle air control? Have you checked the throttle position?

Be carefull CPU runs the idle for the transmission

I get it CPU CPU we replaced a trans was 1st at CPU one of the hardest diagnosis Sometimes CPU did Not sponge a code but it fixed The car

That sounds like throttle body problem. A lot of carbon build up maybe, if so clean throttle body and replace the Idle Air Control (IAC) Valve