P0171 on a 2016 Chevrolet Malibu

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

Ranked from 859 NHTSA owner complaints filed for this vehicle.

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1
External fuel-line or injector leak causing fuel pressure loss
High severity
One complaint reports raw gasoline pooling under the hood with fumes reaching the cabin, and another documents an injector O-ring failure leaking fuel past its seal; a leak like this ahead of the rail can starve the engine of fuel and push the mixture lean.
Reported in 2 NHTSA complaints
Parts:fuel injector fuel line
2
High-pressure fuel pump failure/detachment (GM Recall 18V-358)
High severity
A complaint documents the HPFP's mounting bolts failing and the pump detaching from the cylinder head, with weeks of misfires preceding a P228C fault; reduced fuel delivery from a failure like this can also read as a lean condition.
Reported in 1 NHTSA complaint
Parts:high-pressure fuel pump
3
Misfire-induced lean trim from Stochastic Pre-Ignition (cracked piston)
Medium severity
A complaint ties recurring misfires and a later cracked piston to GM's SPI recall/monitoring campaign on the 1.5L LFV engine; unburned oxygen from a misfiring cylinder can read lean at the O2 sensor and set P0171 alongside the misfire code.
Reported in 1 NHTSA complaint
4
Symptom cluster consistent with a lean-running condition
Low severity
A complaint lists reduced power, poor fuel efficiency, rough idle, poor acceleration, and trouble starting together, a symptom cluster typical of a lean-running engine, though the exact leak point wasn't identified.
Reported in 1 NHTSA complaint
5
Vacuum or intake manifold leak
Medium severity
Unmetered air entering downstream of the MAF is the classic direct cause of a system-too-lean code.
Common cause
Parts:intake manifold gasket
6
MAF sensor fault or contamination
Medium severity
An under-reporting MAF sensor causes the ECU to add less fuel than the engine actually needs.
Common cause
Parts:mass airflow sensor
7
Weak fuel pump or clogged fuel filter
Medium severity
Falling rail pressure under load can't keep pace with injector demand, especially during acceleration enrichment.
Common cause
Parts:fuel pump fuel filter
8
Exhaust leak upstream of the O2 sensor
Medium severity
Fresh air pulled in at a manifold or downpipe leak dilutes the exhaust sample before it reaches the upstream sensor, mimicking a lean condition.
Common cause
Parts:exhaust 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