Originally Posted by STL
p0171 is a lean on bank one, most often caused by a vacuum leak somewhere. Go check all your hoses for crack/dry rot or leaks/holes. and also clean your MAF
(mass air flow sensor)located on the air box
Reset your CEL
by unplugging the battery just turn the headlight switch on for 10 seconds and that will clear it
I too have a check engine light. I just had the engine removed at 100000 for oil pan gasket, RMS, and both Valve cover gaskets (it was leaking oil everywhere!). On the way home from the shop I gased up and then came the light! (I removed and re-installed the fuel cap 4X's). Your method of code clearing sounds promising, but, following the engine removal, my truck was sent by the mechanic to Ford because the PATS
module forgot both key codes and then that theft module was diagnosed as bad (I have NO idea what happened to it) but original mechanic said it was b/c the battery disconnected (I didn't pay for any of this and I got a new truck as a loaner--but I was w/o my Ranger for 3 weeks or more).
My question is if I disconnect my battery, do you think I will have that theft module problem again? (I'm shell-shocked) If so, then maybe I need to let autozone plug in and read/reset the CE Light.