P0171 on a 2015 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 2015 GMC Canyon

Ranked from 318 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Fuel contamination / water intrusion in the fuel system
High severity
One owner documented water in the fuel system that caused injectors to stick open and produced repeated misfires; a fuel system flush plus injector inspection confirms this.
Reported in 1 NHTSA complaint
Parts:fuel injector fuel filter
2
Fuel line/connector leak reducing fuel delivery
High severity
One owner found fuel leaking from the feed/return line connections at the in-tank pump module, which can drop rail pressure and lean out the mixture; also a fire hazard.
Reported in 1 NHTSA complaint
Parts:fuel line
3
Vacuum or intake leak
Medium severity
A cracked hose or loose intake fitting adds unmetered air the ECM cannot account for, especially at idle.
Common cause
4
Dirty or failing MAF sensor
Medium severity
An underreporting MAF causes the ECM to under-fuel; cleaning or replacing the sensor and checking freeze-frame data confirms this.
Common cause
Parts:mass air flow sensor
5
Weak fuel pump or clogged fuel filter
Medium severity
Insufficient fuel volume/pressure under load produces a lean code that worsens with throttle; check fuel trims against a fuel pressure gauge.
Common cause
Parts:fuel pump fuel filter
6
Stuck-open PCV valve
Low severity
A PCV valve stuck open admits excess crankcase air, leaning the mixture particularly at idle.
Common cause
Parts:PCV valve
7
Exhaust leak upstream of the front O2 sensor
Medium severity
Outside air drawn in through a manifold or pipe leak fools the upstream sensor into reading lean.
Common cause
8
Intake manifold gasket leak
Medium severity
A failed gasket lets in unmetered air downstream of the throttle body, a common lean-code source on V6/V8 engines.
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