Trouble code...What's it mean?

Since I put a new clutch in my truck a few months ago, the SES light has gone on and off periodically. When we dropped the tranny rather than take off the whole exhaust we muscled it past the pipe. This brushed by the sensor just behind the cat, and I figured this was the problem all along, I would wiggle the wires and the SES would turn off. Well I scanned it and got DTC code P0137-"O2 SENSOR CIRCUIT LOW VOLTAGE(BANK 1, SENSOR2)" however from what I can gather from my manual, "BANK 1" is the exhaust before the cat. So should I assume this is the sensor in the manifold? Or is there another sensor I don't know about? I'm a bit confused here and was looking for some advice before I start replacing. Thanks for any help.

Bank One Sensor One is the sensor left side drivers side. Check the sensor for fouling, if the senor is bad it usally wont run for crap. I kept getting that code and replaced the sensor with no improvement. Every one was telling me to look for a air leak. Couldnt find one finally I did the the trouble shooter on my Scan Tool it said to check for the rear sensor sensor 3 behind cat. Turned out the rear sensor was bad and throwing the bank one sensor one code. Replaced the #3 Sensor and solved my problem. Sounds like you might have damaged the wires or the sensor .

Year, make, model, & engine would be helpful...my crystal ball broke years ago ;)