1998 Ford F-150 Trouble codes

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P0171/P0174, On many Fords, a P0171 and/or P0174 Lean Code may sometimes appear because of a bad Differential Pressure Sensor (DPFE). This sensor monitors EGR flow, and is located on the engine near the EGR valve. There are two hoses that connect the sensor to the tube that runs from the exhaust manifold to the EGR valve. The sensor misreads EGR flow and the computer increases EGR which has a leaning effect on the fuel mixture. The fix is to replace the DPFE sensor.

Codes P0171 and P0174 for a 1998 Ford F-150 indicate that the engine is running too lean on both banks (Bank 1 and Bank 2) so this happens when there is a vacuum leak or the MAF sensor needs to be replaced in most cases. Please go over this guide as well for more information:

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Here is a guide to help check for a vacuum leak, use when the engine is cold only:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Here is the location of the MAF so you can swap it out to see if it fixes it:

https://youtu.be/ueHWUF6F120?si=ysqAfSqZJyy-qN1W

Please go over these guides and get back to us.