Question

1999 Ford Expedition Eddie bower with code P0171 and P0174

Answer 1

You could start by checking for intake leaks, if no leaks are present you may have to replace the front O2 sensor. Since both codes are present the most likely cause is intake leak.

P0171 FORD - Fuel Injection System Too Lean Bank 1

Read more: https://www.autocodes.com/p0171_ford.html

P0174 FORD - Fuel Injection System Too Lean Bank 2

Read more: https://www.autocodes.com/p0174_ford.html