Car sounds rough. Having idling issues,when starting the car idling at 2500 rpm when it warms up for a few minutes rpms drop to 1000. when turn on the heating/ac the rpms drop lower and sounds like the car wants to stall. Its also having issue changing gears when going up hills. The transmission fluid was change about 8 months ago. I did a obd2 scan the only thing that comes up is 83-11 ECM/ISUFailure.

 

That sounds like a general inspection is needed (or perhaps a fancier code reader). my $115ish buck Innova from amazon has pulled quite a few codes cheap readers have missed. Assuming the car has a bad brain is kinda the last resort, unless you know something we don't.

first thing to check for shifting issues is the fluid!