P0171 on a 2020 Ford F 150 Super Crew

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 2020 Ford F 150 Super Crew

Ranked from 506 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Low fuel rail pressure from a weak or failing fuel pump
High severity
One owner's CEL was tied directly to a fuel-delivery code (P0087) with power loss at high demand, consistent with fuel starvation causing a lean condition.
Reported in 1 NHTSA complaint
Parts:fuel pump fuel filter
2
Exhaust leak upstream of the turbo/manifold skewing sensor readings
Medium severity
An owner documented a factory turbo exhaust-manifold bolt/warping issue causing exhaust leaks on the EcoBoost, which can pull in outside air near the upstream sensor and push fuel trim lean.
Reported in 1 NHTSA complaint
Parts:exhaust manifold gasket
3
Vacuum or intake air leak (cracked hose, loose clamp, intake gasket)
Medium severity
Unmetered air entering after the MAF causes the PCM to add less fuel than needed; smoke-test the intake tract to confirm.
Common cause
4
Dirty or failing MAF sensor
Low severity
A contaminated or drifting MAF undercounts incoming air, causing the PCM to under-fuel; clean or test against known-good values.
Common cause
Parts:mass airflow sensor
5
Stuck-open PCV valve
Low severity
An open PCV valve draws excess unmetered air into the intake, especially noticeable at idle.
Common cause
Parts:PCV valve
6
Intake manifold gasket leak
Medium severity
A leaking intake gasket admits unmetered air directly into the runners, producing a lean bank-specific code.
Common cause
Parts:intake manifold gasket

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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