My check engine light came on, I figured it was an O2 Sensor so had the code pulled. The code is P0174 which I was told was the O2 Sensor but the place I talked to could not tell me which one. How many O2 sensors are there on a 4.6 and does anyone know which one this code is for?

98 F150 Extended Cab
4.6
Auto

 

That code can be set off from a vacuum leak or intake leak. Changing the O2 sensors will not fix it.

 

I have a '98 F150 with a 4.6, and just tackled this problem yesterday. I had codes 171 & 174...fuel sys lean banks 1 & 2. For me, I had a hole in the rubber elbow coming off the PCV valve. I took the neg lead off the battery (to reset the ck eng light), changed out the elbow and have been good for 30 miles so far.
Woo hoo!

 

My 3.0 94 ranger has 2.

 

Vacuum leaks can be the cause of any Rich/Lean codes.