P0171 on a 2016 Chevrolet Malibu Limited

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 Chevrolet Malibu Limited

Ranked from 810 NHTSA owner complaints filed for this vehicle.

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1
Faulty throttle body / intake air-metering system
Medium severity
Two owners had the throttle position sensor and intake airflow system diagnosed as faulty (causing stalling and reduced power); a misreporting air-metering system is a direct contributor to a lean fuel-trim code.
Reported in 2 NHTSA complaints
Parts:throttle body MAF sensor
2
Turbocharger intake/charge-pipe leak (clamp or seal failure)
Medium severity
A dealer diagnosed a turbocharger clamp and exhaust seal failure on this model with a fuel-smell complaint; a boost/charge-air leak downstream of the MAF but upstream of the intake lets unmetered air in and leans the mixture.
Reported in 1 NHTSA complaint
3
Vacuum or intake leak
Medium severity
Cracked PCV hoses, a loose intake boot, or a leaking gasket let unmetered air past the MAF, the classic P0171 root cause.
Common cause
4
Dirty or failing MAF sensor
Medium severity
A contaminated or drifting MAF under-reports incoming air, causing the ECM to under-fuel and trim lean.
Common cause
Parts:MAF sensor
5
Weak fuel pump or clogged fuel filter
Medium severity
Reduced fuel delivery pressure/volume under load can't keep pace with demand, producing a lean condition especially at higher RPM.
Common cause
Parts:fuel pump fuel filter
6
Stuck-open PCV valve
Low severity
A PCV valve stuck open draws excess air into the intake, leaning the mixture at idle.
Common cause
Parts:PCV valve
7
Exhaust leak upstream of the front O2 sensor
Low severity
An exhaust leak ahead of the pre-cat sensor draws in outside air, causing the sensor to report a falsely lean condition.
Common cause
8
Intake manifold gasket leak
Medium severity
A failed manifold gasket is a very common unmetered-air path directly into the cylinders, especially on plastic intake manifolds.
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