Just got my rig back (1/3/14) from the shop for a tranny re-build. Sat for a while (had to make payments). Needed to get a jump, picked it up on a -10 degree day. Ended up needing new battery...NOW O2 sensor (1/2) is reading bad Is this just bad luck or could shop have messed it up? Hoping for a do-it-yourself fix. Is it simple?

 

Perhaps they messed up the sensor when they dropped the trans. Take it back to them and tell them to inspect it. If they damaged it then they should pay for it.