I have a 2002 SC2 and the transmission will go to 4th, but not stay there long. It is like it shifts to 4th on time, but falls out, then struggles to stay in 4th. If on the freeway, it will stay in 4th, but at about 3000rpm. Any Ideas? Maybe a solenoid for the trans? I'm at a loss. Thanks

 

I guess one could start by asking when was the last time the fluid level was checked?

 

Fluids are checked every three weeks, last time being Thursday 8-19.

 

Assuming then that the transmission is in reasonable shape and has been cared for routinely and the fluid itself is not burned which would cause problems with slipping and grabbing (partially similar to what you are describing) and can be identified by something other than a normal red color of the fluid and a decided odor commonly referred to as burnt cork, it gets down to how the transmission works.
It is electronically controlled as you have determined. One of the computors that runs the car also runs the transmission on an as needed basis in part based on how the car is being driven.
My service literature I use to look things up with has multiple pages of information on things to look for.
It requires a scan tool to monitor the computor test port and a series of operational conditions to evaluate with.
Unforunatly the complexity of things of this type are beyond the scope of a forom thread that says hit it with a hammer here and you might fix it.
First of all many of these problems can be asscociated with a bad connection at a plug. Corrosion etc. These can generally be investigated by locating the plugs relating to transmission control and unplugging them and plugging them back in. That action generally will clean corroded pin conections. I usually have a tube of electrical contact grease available at auto parts stores to lube these pin connections. It helps protect from water damage etc. and is applied at the factory and it does not hurt to re-apply it.
I also suggest that you purchase a Saturn self help manual, Chilton, Mitchels and cerainly many others are available and O'Reilly or Autozone usually carry these. It may also help to have access to a scan tool to aid in trouble shooting. Instructions on how to use it will be in the servicening literature. The tools can be purchased for about $100.00 or so at this point in time.
Expensive? Yes, but cheaper than pissing money away buying parts and installing them that you do not need.
How many times do you need them? If only once, they have paid for themselves the first time you use them and at the present all automotive Electronic packages can be validated using the same tool I believe so it will be a while before it is out dated.
Maybe some one can point you at a specific thingy that might cause a problem. I can not. I would have to go look for it using these tools.
So, check for burnt transmission fluid, find connectors that might be corroded and buy your self some service literature.
And go from there.