P0134 check engine after starter change in my 99 Lanos

[chriscomputers]

So this past weekend I changed my starter. About 30 minutes after I start driving the check engine light comes on and I now have a P0134 oxygen sensor code. Anyone have any ideas of what happened? Could I have bumped something? I checked the wiring for the 02 sensor and it is all hooked up. Is there maybe something on the rear of the engine near the starter that I may have nudged that is messing with the circuit? My 02 sensor is only 2 years old.

[woo99SE]

p0134 is for upstream O2 sensor, the one before the cat conv. check the plug, release it and plug it back on, clear the code and restart the car.
check for codes.