P0171 on a 2016 Ford F 250 Supercab

P0171 means the engine computer is adding more fuel than normal on bank 1 because it sees too much air or not enough fuel.

Not your vehicle? See general P0171 info.

Most common causes on the 2016 Ford F 250 Supercab

Ranked from 287 NHTSA owner complaints filed for this vehicle.

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1
Restricted fuel supply from a clogged fuel filter
High severity
One owner's fuel filter clogged badly enough to spray fuel from the top of the filter housing, showing how a partially restricted filter starves the engine of fuel and drives the mixture lean.
Reported in 1 NHTSA complaint
Parts:fuel filter
2
Failing lift pump or high-pressure fuel pump
High severity
A fuel pump that failed outright caused a sudden loss of power in one truck; a fuel-pressure shortfall under load is a leading cause of a lean-condition code on diesels.
Reported in 1 NHTSA complaint
Parts:fuel pump
3
Vacuum/charge-air intake leak
Medium severity
A leak in the turbo boost tract or intake between the MAF and the intake manifold lets unmetered air in, leaning the mixture.
Common cause
4
Dirty or failing MAF sensor
Low severity
A contaminated or drifting MAF undercounts intake air, so the PCM adds less fuel than actually needed.
Common cause
Parts:mass airflow sensor
5
Stuck-open crankcase ventilation (CCV) valve
Low severity
An open CCV valve draws extra unmetered air into the intake tract, similar to a gas-engine PCV leak.
Common cause
Parts:crankcase ventilation valve
6
Exhaust leak upstream of the oxygen/wideband sensor
Medium severity
An exhaust leak ahead of the sensor draws in outside air, making the PCM see a falsely lean exhaust reading.
Common cause
7
EGR cooler or valve leak skewing intake air metering
Low severity
A leaking EGR cooler or stuck valve changes the actual air charge without the PCM knowing, throwing off the fuel trim calculation.
Common cause
Parts:EGR valve

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0171 on your car still needs shop confirmation before any repair.

Common symptoms

Check engine light
Rough idle
Hesitation
Surging idle
Poor fuel economy

What to check before replacing parts

Review short- and long-term fuel trims on bank 1

Look for: High positive trims (commonly worse at idle, improving with RPM) mean the computer is adding fuel to compensate for excess air or insufficient fuel — that pattern is this code's fingerprint.

Smoke-test the intake

Look for: Smoke escaping (or a hiss you can hear) at intake boots, gaskets, or vacuum hose connections confirms unmetered air is entering after the MAF sensor, which is the most common cause of a lean code.

Inspect the PCV hoses and valve

Look for: A cracked, split, or disconnected PCV hose, or a PCV valve stuck open, draws in extra unmetered air the same way a vacuum leak does.

Clean and test the MAF sensor

Look for: Visible dirt or oil film on the sensor element, or a grams/second reading that doesn't track expected airflow for RPM, means the MAF is under-reporting air and causing the computer to under-fuel.

Verify fuel pressure

Look for: Pressure below spec (weak pump, clogged filter, failing regulator) starves the engine of fuel and produces the same lean trim pattern as a vacuum leak — rule it out before chasing leaks.

Rather have a pro handle it? Find a vetted local mechanic.

Matching symptoms

Car Runs Rough