P0171 on a 2017 Ford F 250 Regular Cab

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 2017 Ford F 250 Regular Cab

Ranked from 1,155 NHTSA owner complaints filed for this vehicle.

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1
Failing high-pressure fuel pump (CP4) causing chronic low fuel pressure
High severity
This is an overwhelmingly documented failure on this exact truck: repeated "Low Fuel Pressure"/reduced-power events and confirmed high-pressure fuel pump failures (with metal debris) across many owners, directly matching a system-too-lean fuel-delivery fault.
Reported in 7 NHTSA complaints
Parts:high-pressure fuel pump fuel filter
2
Cracked or leaking fuel filter housing/fuel lines
High severity
Multiple owners on this vehicle report the fuel filter housing or fuel lines cracking and leaking, matching an NHTSA-tracked Super Duty fuel-filter-housing issue and reducing usable fuel pressure/volume.
Reported in 3 NHTSA complaints
Parts:fuel filter housing fuel line
3
Loose or disconnected fuel filter/line fitting
Medium severity
Two owners report a fuel filter hose/fitting coming loose and dumping fuel/air into the system, which will disrupt commanded fuel pressure.
Reported in 2 NHTSA complaints
Parts:fuel line
4
Defective/failing intake manifold
Medium severity
Two owners on this vehicle had a defective intake manifold diagnosed, a source of unmetered intake air.
Reported in 2 NHTSA complaints
Parts:intake manifold
5
Fuel pump losing prime due to a faulty check valve
Medium severity
Owner reports the fuel pump losing prime at the rail due to a faulty check valve, a known revision issue on this platform.
Reported in 1 NHTSA complaint
Parts:fuel pump
6
Vacuum or intake leak
Low severity
A cracked hose or intake gasket admits unmetered air, producing a lean condition.
Common cause
7
Dirty or failing MAF sensor
Low severity
A contaminated or drifting MAF sensor under-reports incoming air, causing the ECM to under-fuel.
Common cause
Parts:mass airflow sensor
8
Exhaust leak upstream of the sensor
Low severity
A leak ahead of the sensor draws in outside air and biases the reading toward lean.
Common cause

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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