Well heres my dilemma, my Saturn SC2 was giving.

Well heres my dilemma, my Saturn SC2 was giving me a random check engine code, when the car turned off to check the code, it was gone no code and starting the car again showed no code. Now fast forward a few months check engine light starts coming on after about 10 minutes of driving or roughly when the car hit the halfway on the temp gauge. Before this happens shifting past third gear is rough, AFTER these limits one or the other are hit it will NOT shift past third and it gets stuck In third and revs real high almost 5 to 7 rpms, or if I try ignoring it, it shifts into first with low power and almost red line rpms. Now i'd believe this is a transmission problem BUT if I pull over and turn the car off and re start it. No check engine code and no trans problem. Upon searching sights like this it struck me there was a common ground to my problem that was worth replacing. The (ECTS) engine coolant temp sensor. Reason being that in my Saturn it measures the engine coolant temp and the transaxle parameters and hell for $13 it was worth a shot. NOW after replacing it the car seemed to run better it shifts much quieter with no reverse slam. However the same problem started occurring more rapidly as a matter of a few days went on. This cars in pretty good shape and I don't personally think its worth scrapping i'm hoping there is just something I am over looking
PLEASE HELP?