P0171 on a 2015 Chevrolet Equinox

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 Equinox

Ranked from 678 NHTSA owner complaints filed for this vehicle.

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1
PCV System Failure and Blown Engine Seals (Vacuum Leak)
High severity
A clogged or malfunctioning PCV system causes excessive crankcase pressure, blowing out the rear or front main seals. This creates a massive vacuum leak as unmetered air is drawn into the engine, triggering a lean code.
Reported in 5 NHTSA complaints
2
Cracked Exhaust Manifold
Medium severity
A cracked exhaust manifold allows unmetered ambient air to enter the exhaust stream before the upstream oxygen sensor. The sensor misinterprets this extra oxygen as a lean running condition.
Reported in 1 NHTSA complaint
3
Failing Fuel Pump / Low Fuel Pressure
High severity
If the fuel pump fails to deliver adequate pressure or volume to the engine, the air-to-fuel ratio becomes too lean. A fuel pressure test will confirm if the pump is meeting specifications.
Reported in 1 NHTSA complaint
4
Clogged or Faulty Fuel Injectors
Medium severity
Restricted fuel injectors fail to spray the commanded amount of fuel into the combustion chamber, leading to a lean condition on the affected bank.
Reported in 1 NHTSA complaint
5
Dirty or Faulty Mass Air Flow (MAF) Sensor
Low severity
A contaminated MAF sensor under-reports the amount of air entering the engine. The PCM then commands less fuel than actually needed, resulting in a P0171 code.
Common cause
6
Intake Manifold or Vacuum Hose Leaks
Medium severity
Cracked vacuum lines or a degraded intake manifold gasket allow unmetered air into the intake tract. A smoke test of the intake system will reveal the leak source.
Common cause
7
Faulty Upstream Oxygen (O2) Sensor
Low severity
A degraded or biased upstream O2 sensor may falsely report a lean condition to the PCM when the actual air-fuel ratio is normal. Live data monitoring of the sensor's voltage switching is required to confirm.
Common cause

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.

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Matching symptoms

Car Runs Rough