i gave the 98 cavalier to my daughter and its been doing well until a few days ago. it is showing po121 throttle/pedal position sensor/switch a circuit range when i scanned it.i cleared it and the code came back. i believe it needs a tps but what confuses me is she said when the cel came on her auto trans stated slipping. i drove the car and found harsh shifts and a bit of slipping when gearing down. could this just be the ecu not knowing where the throttle is actually at or is it because it is in limp mode? anyone else had this problem? it has no more codes so should i just replace the tps? i don't think adjusting it would help because nothing has moved it. please correct me if i am wrong , i am just praying the trans isn't going as it doesn't slip once its in gear. - idk.thanks all -Ted

What do you mean "slipping when gearing down"? To my knowledge, automatics don't down @!#$, unless you mean when its floored and it revs high to really pick up speed? If its the flooring thing, i can see that having sometihng to do with the TPS.

passing gear. i put lucas trans treatment in it and changed the tps and problem solved. thanks all.