Perplexed

[LarryIII]

I have an interesting problem. I drove my 97 SVX LSi to work this morning with no peoblems. I parked in the open air garage on the ground floor of the building where I work. The car has 49,000 miles on it.

Tonight when I left work I started up the car and let it warm up.
The 'Check Engine' light stayed on. I shut it off and restarted the car. The light stayed on again. I popped the hood and checked the oil. I 'd say it was about 1 quart low. I restarted the engine and let it come up to normal temperature. The engine idled as always and was very quiet as usual. When the engine was fully warmed up I shut it off and checked the oil level again. It was the same as before. The engine idled smooth as silk. I decided to go home. I drove slow in traffic and reached home. The 'Check Engine 'light stayed on the whole way. I put the car in our garage and put about 1 1/2 quarts of Mobil 1 in it. It is slightly over-full now. The light stayed on. I'm perplexed. There doesn't seem to be anything wrong with the engine. Could it be the sensor? Does anyone have any ideas and/or suggestions?

PS: There are no indications of any leaks and the exhaust is clean.