My 04 D2 has 115k on it. Replaced both of my up stream O2 yesterday. Was throwing a couple of codes, and realized that the connection was not fully seated on the passenger side. Got them connected, thought it was all good. Not the case, I'm throwing a P0150 code now. When I start the car I watch my UG, it seems okay then the Bank 2 front sensor shows a declining voltage to 0.0000, and thus tripping the code. I re-cleaned everything with a liberal dose of electronics cleaner, and put it back together. No joy. Having read that there might be a crimped broken wire, i played with the wiring, just pushing it a little to see if it helped, no dice.
I'm thinking the sensor is bad (I have read here that it happens with the BOSCH ones). New one on the way. While I am waiting, does anyone want to chime in on other possibilities for this?

 

I was going to suggest swapping the two upstream and seeing if the code changed to the other bank. Then you would know if o2 was bad.