Thermostat and Check Engine Woes

So, I replaced my Tstat and ran her last night. Everything was fine as expected.
On the way to work this morning, the check engine light popped on. I imediatly scanned my gauges. The only thing odd was the coolant temp seemed slightly cooler than what I remember.
Ran fine though. No odd smells or sounds.
Any ideas?

If the computor does not read the correct coolant temp in a certain time period it will trip the CEL.You may have had air in the system or still have an air pocket.It may be possable that the thermostat is not seated in the block correctly (slipped out of the groove in the block)and was tightened down without leaking or cracking the housing.I had the slip out thing happen to me with the same results you have.
Wayne

Right on. Thanks for the ideas to check for. I should just keep a plethora of gaskets around. lol

Hmm, interestingly enough, when I started it up just now, the check engine light is still on. Shouldn't it be back off after sitting for a long period?

no, the code will stay stored. Disconnect the negative post on your battery for a min and it will reset

LOL. Silly Jeeps. Ok, Thanks much.