psi2high

My friend recently swapped his em1 and found a broken wire to the o2 so he soldered it back together but now its throwing a code for high voltage in bank 1. I have a spare engine harness for an ob2b car but is it the chassis harness or the engine harness that would need to be replaced? And would soldering the wire cause some sort of resistance causing it to throw the code? The o2 sensor is brand new new by the way.
Thanks
Sean