Hey MNF150Sport, I'm about 470 miles northwest of you and so I know about it being c-c-c-cold. A couple of things I can comment on: 1) it seems weird that you're getting both lean and rich codes at the same time. Never heard of that before, but I note that Christian Hunter has the same thing. 2) On my '99 4.2l, I had codes P0171, P0174, P1131, P0133, and P1132. I ended up replacing the fuel pump (big repair, had no choice after it died - and because most of the codes came back after replacement I doubt it was the cause of any), the infamous rubber elbow under the throttle body, and the upstream 02 sensors. Have had no codes since. 3) The previous owner of my truck drove it with the service engine soon light on for quite a while and it took me some time to remedy everything.There was no damage to the engine that I am aware of. 4) No, I don't expect that these codes have anything to do with the cold but again, how is it that you're getting 'lean' and 'rich' simultaneously? Someone with more knowledge than I will have to answer that one. Anyway, best of luck with it.

 

Say JBrew, I was typing my response to the OP and saw your post after I submitted. Good information to remember and makes good sense that contradictory readings point to 02 sensors that are done like a prairie dinner.

 

Yea, I've been on 150 sites since around 05. The lean and rich DTC's on the same O2 has come up before, it's not common but always ends up an O2 failure.

What I haven't seen is both upstream O2's failing like that at the same time. That's a little strange; it might make more sense knowing the history...what lead up to it. However, an O2's life span is short under a consistently rich condition. Like say, running with misfires for a long period of time.