P0171 on a 2015 Chevrolet Suburban 1500

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 Chevrolet Suburban 1500

Ranked from 428 NHTSA owner complaints filed for this vehicle.

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1
Chafed/leaking plastic fuel feed line (GM TSB 17-NA-304)
High severity
The fuel feed line rubs against the frame near the tank and wears a pinhole; the resulting fuel pressure/delivery loss is a documented, very common cause of a lean code on this generation Suburban, and is by far the dominant complaint pattern for this vehicle.
Reported in 13 NHTSA complaints
Parts:fuel feed line fuel line clips/retainer
2
Weak or leaking fuel pump / low fuel pressure
Medium severity
One owner reports a failing brake vacuum pump alongside a fuel pump/vacuum leak causing a gas smell; insufficient rail pressure produces a lean condition under load.
Reported in 1 NHTSA complaint
Parts:fuel pump
3
Vacuum or intake leak
Medium severity
Unmetered air entering after the MAF sensor is the single most common cause of a system-too-lean code; check intake boots, PCV hose, and brake booster line.
Common cause
4
Dirty or failing MAF sensor
Medium severity
A contaminated or drifting MAF under-reports incoming air, so the PCM adds less fuel than the engine actually needs.
Common cause
Parts:mass air flow sensor
5
Clogged fuel filter
Medium severity
Reduced flow to the rail under load causes fuel pressure to sag exactly when the engine calls for more, producing a lean code at higher RPM/load.
Common cause
Parts:fuel filter
6
Stuck-open PCV valve
Low severity
A PCV valve stuck open pulls excess, unmetered crankcase air into the intake, leaning the mixture.
Common cause
Parts:PCV valve
7
Exhaust leak upstream of the O2 sensor
Low severity
Outside air drawn in through a manifold or downpipe leak skews the upstream O2 reading lean even though the actual mixture is correct.
Common cause
8
Intake manifold gasket leak
Medium severity
A failed gasket lets outside air bypass the MAF directly into the plenum, a classic lean-code cause on GM V8s.
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