P0171 code
 

Truck just threw a P0171 code the other day. I have a 04 f150 with a custom 89 tow tune that I run all the time. I just got the tune 1 month ago, do you think its the tune thats causing the code? Should I return the truck back to stock. Truck has never had any problems and I didnt notice any performance issues.

It's telling you the oxygen sensor on the passenger side has detected a "lean" condition. These are common causes:

The MAF (Mass Air Flow) Sensor is dirty or faulty. If you have an "oiled" air filter it could foul the MAF sensor if the filter is over-oiled.

A vacuum leak downstream of the MAF sensor can cause this too, but I doubt this is the problem.

My money is on the MAF sensor, given the age of your truck. When was the sensor last cleaned? I really doubt it's the tune.

Here's a link to cleaning the sensor: How to Clean MAF-2005 5.4 - F150online Forums Notice it's for an 05 model, but I think the 04s are the same.

- Jack

Thanks for the tip. The truck has 61000 miles on it. To my knowledge the sensor has never been cleaned. I dont run an oiled air filter but I will clean the sensor. Should I clear the code and see if it comes back? How long does a code usally take to come back if there is a problem? Thanks

Certainly you should clear the code. You can do it right away. I really don't think Bill will have given you a tune that's too lean. He's been writing tunes for 04 trucks for a long time now. As you can see, my truck's an 05, which is VERY similar to yours and I've never had this problem. Supposedly though, the dealership I have my truck serviced at has performed the MAF sensor cleaning. I suppose one day I should check it myself, but "if it ain't broke..." :)

I used to do almost all my vehicle maintenance. Now, I save that effort for my trailer, which is more than I expected.

- Jack

I'll add some more....

While you're cleaning your MAF .....
Clean your TB.
Change your fuel filter.