P0171 on a 2017 Ford F 150 Crew 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 150 Crew Cab

Ranked from 1,066 NHTSA owner complaints filed for this vehicle.

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1
Intake manifold gasket / runner control failure
Medium severity
Two complaints describe a known intake manifold runner control fault on this truck series (stuck runner, SES/LIMP mode) that can allow unmetered air and skew fuel trims lean.
Reported in 2 NHTSA complaints
Parts:intake manifold intake manifold gasket
2
Weak fuel pump or fuel delivery interruption
Medium severity
Insufficient fuel pressure/volume under load produces a lean condition; one complaint describes the truck dying at low speed/idle with pre-stall shaking, consistent with a fuel delivery lapse.
Reported in 1 NHTSA complaint
Parts:fuel pump
3
Vacuum or intake air leak
Medium severity
A leak after the MAF (hose, gasket, PCV line) is the most common cause of a lean bank-1 code and is the first thing to smoke-test.
Common cause
4
Dirty or failing MAF sensor
Medium severity
A contaminated or drifting mass airflow sensor under-reports incoming air, causing the ECM to under-fuel.
Common cause
Parts:mass airflow sensor
5
Stuck-open PCV valve
Low severity
A PCV valve stuck open draws excess unmetered air into the intake, especially noticeable at idle.
Common cause
Parts:PCV valve
6
Exhaust leak upstream of the bank-1 O2 sensor
Low severity
A leak ahead of the sensor draws in outside air, making the ECM read the exhaust as leaner than it actually is.
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