Temp Gauge not working & Check light on

I have a 2001 2.2 L auto - I was doing some brake maintenance today and kinda a 50 K mile tune up and after I headed out after finishing it all my temp gauge in the dash went to the resting position, ceased to work, (100 F) and the Service Engine light came on. I had the plastic air box assembly, before the carb, off and was all my sensors were in that area (I think 4) were dissconnected while putting in new plug wires, but were reconnected before reassembling everything and closing the hood. I drove about an hour like this on the highway back home, did not notice any drop in preformance or anything unusual. After about 2 hours I went out popped the hood and checked all the sensors that I had disconnected, pulled them all off and then reconnected them. I also checked under the access flap in the passenger wheel well where I was messing around by the ignition modules becuase there are two sensors going into the bottom of the block down there that come really tight up against the conduit of the pluge wires and those wires, although tight, were not dissconnected. Any ideas? Ill probably just get the code downloaded but I cant find any sensors disconnected, and the light usually goes away if it is fixed (happens all the time with the gas cap not being properly sealed).

Thanks