O2 sensor
 

While searching for oil leaks I found that one of the four wires (the black one) to the O2 sensor was disconnected. This sensor apparently did not come with matching connectors so omeone had cut off the orginal connectors and used cheap crimp-ons. Anyway I reconnected the wire. Does anyone know if the sensor could have been damaged by this. The Check engine light has been on since I bought the car, and I haven't checked the codes yet, but I guessing their related.

RE: O2 sensor
 

It could have but most likely not. The only way to find out for sure is to pull the codes and reset and see if they come back.