I've searched through the forums here and think I have a general idea of where to look.
We just had the head gaskets replaced on our 1999 Forester with 125,000 miles. Car was going through coolant and oil at a rediculous pace. Prior to the repair, there were no trouble codes. We got the car back this past Thursday and it runs great. Last night, however, the CEL light came on and when I scanned it, I got P0133, O2 sensor circuit, Slow Response Bank 1, Sensor 1. The car is now idling rough but didn't prior to the code appearing.
I've found out this O2 sensor is on the right side of the car prior to the cat. Could the excessive coolant and oil usage caused the sensor to act up and cause this code to appear? I haven't had a chance to check the wiring or the connector yet, perhaps the shop forgot to plug the sensor back in. I can't hear any exhaust leaks. Am I on the right track here? Anything else I should look for/at? Thanks!