P0171 on a 2016 GMC Canyon

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 Canyon

Ranked from 267 NHTSA owner complaints filed for this vehicle.

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1
Chafed fuel line / leaking fuel supply (missing skid plate or AC-line contact)
High severity
Separate owners found fuel leaking from a hose rubbing on the AC compressor line and from a fuel tank missing its skid plate; both reduce delivered fuel pressure enough to trigger a lean condition.
Reported in 2 NHTSA complaints
Parts:fuel line fuel tank skid plate
2
Rodent-damaged fuel/vacuum line
High severity
Soy-based line insulation on this truck attracts rodents; one owner found a fuel line chewed through causing a significant leak, a direct, well-documented lean-code cause on these trucks.
Reported in 1 NHTSA complaint
Parts:fuel line
3
Fuel delivery/metering fault sensitive to fuel octane
Medium severity
One owner reports a consistent miss/hesitation while cruising that is 90% reduced on premium fuel, consistent with a marginal lean condition being pushed over threshold by lower-octane fuel's combustion characteristics.
Reported in 1 NHTSA complaint
Parts:fuel injector
4
Vacuum or intake leak
Medium severity
The most common general cause; unmetered air entering after the MAF sensor leans the mixture at idle and cruise.
Common cause
5
Dirty or failing MAF sensor
Medium severity
Under-reports incoming airflow, so the PCM commands less fuel than needed.
Common cause
Parts:mass air flow sensor
6
Stuck-open PCV valve
Low severity
Pulls extra unmetered air into the intake, leaning the mixture especially at idle.
Common cause
Parts:PCV valve
7
Intake manifold gasket leak
Medium severity
Lets outside air bypass the MAF directly, a classic lean-code source.
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