P0171 on a 2016 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 2016 Ford F 150 Super Crew

Ranked from 1,686 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Exhaust manifold leak / loose or cracked manifold upstream of the O2 sensor
Medium severity
Recurring complaint on this truck — cracked manifolds and backed-out/broken manifold bolts (a known factory torque issue) leak exhaust ahead of the sensor, drawing in outside air that reads as lean; look for soot streaking and a high-pitched exhaust whistle.
Reported in 3 NHTSA complaints
Parts:exhaust manifold gasket exhaust manifold bolts exhaust manifold
2
Weak or failing fuel pump causing lean stall at low fuel level
Medium severity
Reported on this truck as engine stall at 1/4 tank or less in stop-and-go traffic, related to the fuel pump/pickup issue covered by later F-150 recall #25S75; check fuel pressure/volume holds steady as the tank runs low.
Reported in 1 NHTSA complaint
Parts:fuel pump
3
Vacuum or intake leak
Medium severity
Unmetered air entering downstream of the MAF leans out the mixture; smoke-test intake boots, PCV hoses, and vacuum connections.
Common cause
4
Dirty or failing MAF sensor
Medium severity
A contaminated or drifting MAF under-reports incoming air, causing the PCM to under-fuel; inspect the element and compare live MAF data to expected values.
Common cause
Parts:mass air flow sensor
5
Stuck-open PCV valve
Low severity
An open PCV valve draws excess unmetered air into the intake, leaning the mixture especially at idle; check for a valve stuck open or a collapsed hose.
Common cause
Parts:PCV valve
6
Intake manifold gasket failure
Medium severity
A leaking manifold gasket admits unmetered air directly into the intake runners, often producing a cylinder-specific lean condition; smoke-test the manifold.
Common cause
Parts:intake manifold gasket
7
Clogged fuel filter
Low severity
Restricted fuel flow under load starves the injectors and leans the mixture as RPM/load increases; check fuel pressure drop under load.
Common cause
Parts:fuel filter

Part links go to Amazon search results for this vehicle. As an Amazon Associate, WrenchConnect earns from qualifying purchases — always confirm fitment for your exact trim and engine before ordering.

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