P0171 on a 2016 GMC Yukon

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 GMC Yukon

Ranked from 265 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Fuel delivery leak or weak fuel pump
High severity
Owners reported a chafed/leaking fuel supply line and a leaking fuel pump producing rough running, gas smell, and misfire consistent with low fuel pressure.
Reported in 2 NHTSA complaints
Parts:fuel pump fuel supply line
2
Failing or clogged fuel injector(s)
Medium severity
One owner's Yukon needed fuel injector replacement after a dealer-diagnosed misfire with rough idle and jolting acceleration, consistent with injectors under-delivering fuel.
Reported in 1 NHTSA complaint
Parts:fuel injector
3
Vacuum or intake air leak
Medium severity
Unmetered air entering through cracked intake boots, PCV hoses, or brake-booster lines skews the air/fuel ratio lean; listen for a hiss and smoke-test the intake.
Common cause
Parts:intake boot vacuum hose PCV hose
4
Dirty or failing mass airflow (MAF) sensor
Medium severity
A contaminated or drifting MAF sensor under-reports incoming air, causing the PCM to lean out fueling; clean or test with a scan tool.
Common cause
Parts:mass airflow sensor
5
Stuck-open PCV valve
Low severity
A PCV valve stuck open draws excess air into the intake at idle, leaning the mixture; check for a valve that rattles or won't seat.
Common cause
Parts:PCV valve
6
Intake manifold gasket leak
Medium severity
A worn intake gasket lets in unmetered air, most noticeable at idle; smoke-test the manifold for leaks.
Common cause
Parts:intake manifold gasket
7
Exhaust leak upstream of the front O2 sensor
Low severity
A leak ahead of the sensor lets in outside air and skews the reading lean; inspect the exhaust manifold and gaskets for cracks or soot streaks.
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