OBD codes / P0171 / Ford F-150
P0171 on a Ford F-150
System Too Lean (Bank 1)
5.4L/4.6L Triton V8s and 3.5L/2.7L EcoBoost V6 (bank 1).
What P0171 usually means on a F-150
P0171 means bank 1 is running lean, with the PCM adding fuel to compensate for extra unmetered air or too little fuel. On the F-150 the common causes are vacuum and PCV leaks, a dirty mass airflow sensor, and on EcoBoost trucks boost-side leaks or a weak fuel supply. A lean bank-1 code often comes paired with its bank-2 twin when the cause is shared, like a MAF or intake leak. Symptoms range from none to a rough idle, hesitation, or a slight power loss.
Most likely causes on this model
- Vacuum or PCV leak
Cracked PCV hoses and intake gaskets are a leading lean-code cause on aging Tritons, letting in unmetered air that leans out bank 1.
- Dirty or failing mass airflow sensor
A contaminated MAF under-reports airflow so the PCM under-fuels, setting P0171. Cleaning or replacing the MAF is a common cure across the F-150 range.
- Boost or intake leak (EcoBoost)
On turbo trucks a loose intercooler coupler or cracked charge pipe leaks metered air after the sensor, driving fuel trims lean under load.
- Weak fuel delivery
A tired fuel pump, clogged filter, or dirty injectors can starve the bank enough to log a lean code, particularly under towing loads.
What it costs on a F-150
Most P0171 fixes on the F-150 are inexpensive: a MAF cleaning, a PCV hose, or a charge-pipe clamp costs little in parts. Smoke-testing for leaks is a modest diagnostic charge that saves money by finding the exact source. It only gets pricey if the cause turns out to be fuel-pump or injector work, so confirm the cheap items first.
Fixing it
Check fuel-trim data and smoke-test the intake and (on EcoBoost) the charge pipes before replacing parts. Clean or replace the MAF and cure any vacuum/PCV leaks first, since those are the usual culprits.
For the full step-by-step diagnosis order (any vehicle), see the main P0171 guide.
Year, engine and mileage change the answer. Get a diagnosis for your F-150 — it weighs these causes against your exact configuration and real complaint data.
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Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0171 behavior is covered on the main P0171 page. Confirm with a scan tool before buying parts.