2002 Saturn SL1
81k Miles
No previous problems until this light came on.

I had the light diagnosed at Auto Zone and it came back with 2 different problems.

#1
IAC circuit condition or idle speed higher/lower than expected.
The ECM has detected that the IAC counts are higher or lower than expected, the engine speed is not in it's expected range.
Probable Causes: Vacuum leak on engine, dirty throttle body, IAC motor defective, poor electrical connection.

I didn't think these cars had an IAC or throttle body since they are fuel injected. Anyways, I haven't noticed anything strange about the idle. The cars runs smooth.

#2
Coolant temp is always low.
Probable Causes: check coolant level, thermostat defective, ECT sensor defective.

The coolant did seem low. The engine was warm when I checked and the level was at the lowest allowed cold engine level, so I added some.

I also checked the oil and it took about 1.5 quart to get back up in the full range.

I then disconnected the battery for 15 minutes, reconnected, and haven't seen the light again yet.

Everything seem ok?

#1 : Bad intake manifold gasket. Notorious for 3rd gen SOHC s-series. Spray brake cleaner near the intake gasket around each cylinder especially cyl #1. You will notice a change in the idle---> proves the gasket is leaking. Search here for a How-to with pictures...Quite an easy job that can be done saturday afternoon.

#2 : Add more coolant! Which you did so you should be good to go. Normal operating temps for your car are 1-2mm above 1/4 as per the gauge :)