THis has happened twice now. One day, the check engine light came on and the temperature gauge was dead. Runs fine for a day or so. Then won't start. Actually, may be that it won't start when it's hot. The first time I drove it for a bit, shut it off to fill the gas tank, and it wouldn't re-start. This time, similar thing.
Brought it in the first time. They said the no-start was unrelated to the temp gauge. Said the gauge was just unhooked and blamed the no-start of a dirty fuel system.
Ran fine for a month or so. Now same thing. Gauge dead, check engine light on. Tarted it up this morning, drove it for a few minutes. Engine of. Wouldn't re-start.
Check the connection for the ECTS (coolant temp sender). The sensor coul be bad also but I believe that 2002 model saturns had the new and improved brass tip design. The old plastic tipped ones always failed with age.
If it is is disconected or dirty/damaged it tells the computer it is like 70 below or so. The PCM then will give the engine a lot of gas that it does not need when it is warm. It would also explain the dead temp gauge.
Get the codes read and post back. : )
Some large chain auto parts house will do this for free.