P0171 code

[Jackpine]

Originally Posted by morfn321

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