Question

2001 Ford Ranger XLT 4.0L with engine codes P0171 and P0174, what do the codes mean?

Answer 1

P0174 Fuel trim lean Bank 2

P0171Fuel trim lean Bank 1

A lot of causes for a fuel trim lean can come from anywhere, when there a fuel trim that's lean what to look and listen for is vacuum leaks, Vacuum leaks are air that gets pass the MAF (Mass airflow) and is not accounted for. Here are some of the most obvious to the not so obvious Lean fuel Trim causes

A good MAF air duct tube should be no tears or cranks

A broken MAF airflow tube where the tape was used to seal a false air leak, which did not succeed.

Here on a 4.0 the intake manifold upper and lower gasket was the cause for lean code conditions.

Answer 2

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