P0171 on a 2015 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 2015 Ford F 250 Supercab

Ranked from 296 NHTSA owner complaints filed for this vehicle.

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1
Fuel starvation/contamination from failing high-pressure (CP4) pump
High severity
This truck's known CP4 pump failure mode contaminates and can starve the fuel system, producing a low-fuel-pressure/lean-running condition alongside the more dramatic failure complaints.
Reported in 4 NHTSA complaints
Parts:high-pressure fuel pump fuel filter fuel injectors
2
Cracked fuel filter housing or corroded fuel line causing air ingestion
Medium severity
Owners report a cracking upper fuel filter housing and a rusted/leaking fuel line that let air into the supply side or restrict delivery, both of which starve the engine and can register as a lean condition.
Reported in 3 NHTSA complaints
Parts:fuel filter housing fuel line
3
Charge-air (boost) system leak
Medium severity
A split intercooler hose or boost tube lets metered air escape after the sensor, making the engine run leaner than commanded.
Common cause
Parts:intercooler hose boost tube
4
Failing or dirty mass airflow (MAF) sensor
Medium severity
A drifting MAF signal under-reports intake air, so the PCM commands less fuel than the engine actually needs.
Common cause
Parts:MAF sensor
5
Weak fuel lift pump or clogged fuel filter
Medium severity
Reduced supply pressure/volume to the high-pressure pump leaves the engine fuel-starved under load.
Common cause
Parts:fuel lift pump fuel filter
6
Exhaust leak upstream of the oxygen/wideband sensor
Low severity
Outside air drawn in through a manifold or downpipe leak skews the sensor toward a false lean reading.
Common cause
7
Stuck-open or leaking EGR valve
Low severity
Unmetered air entering through a leaking EGR passage dilutes the intake charge and can read lean.
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