Hi folks. Dakota 2000 V8 4.7L, 155k, no custom work, everything standard.

The truck has become a backup vehicle and work around the house truck so it doesn't get driven much. But the other day I noticed that the gas mileage (according to the onboard computer) was dropping to around 10mpg. I kept resetting the computer thinking that maybe it was messing up but soon afterwards the check engine line came on.

Was passing an Advance Auto so swung in to get it read it came up a P0171, Lean 1/1. So after a bunch of research and inspecting the truck I see that the power steering pressure switch has gone bad and has been leaking fluid down the wiring harness and has reached the O2 sensors. I'm sure its well past time to replace those bad boys but to start with I've replaced the PS switch and cleaned out the electrical clips on the O2 sensors. Then reset the P codes.

Drove the truck out to the store, put in a bottle of fuel treatment and drove around for a while. The check engine light has remained off and no more P codes but the mileage is still poor. Now the whole time I'm still getting good response from the throttle, good power, no black soot out of the tail pipe. If it weren't for the computer telling me that the mpg were very low, I'd never know anything was wrong.

Any recommendations on what to focus in on? If the O2 sensors were faulty or bad shouldn't I be getting a P code on those?

 

check to see if excess fuel has gone into the crankcase. this could damage the engine