P0171 on a 2010 Chevrolet Silverado 1500 Extended Cab
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 2010 Chevrolet Silverado 1500 Extended Cab
Ranked from 422 NHTSA owner complaints filed for this vehicle.
- 1
Intake manifold gasket leak (vacuum leak)
Medium severityGM Gen IV 5.3L Vortec engines of this era are well known for intake manifold gasket leaks that create an unmetered-air lean condition; one owner replaced plugs, coils and injectors chasing a persistent cylinder-6 misfire without success, a pattern consistent with an unresolved vacuum leak rather than ignition parts.
Reported in 1 NHTSA complaintParts:intake manifold gasket - 2
Failing or dirty MAF/MAP sensor
Medium severityAn inaccurate airflow or manifold-pressure reading skews the commanded fuel trim lean; one owner had the mass airflow and MAP sensors replaced while chasing an intermittent limp-mode check-engine fault.
Reported in 1 NHTSA complaint - 3
Exhaust leak upstream of the front (bank 1) oxygen sensor
Medium severityBroken exhaust manifold bolts are a documented issue on GM Vortec V8 trucks of this generation; the resulting leak draws outside air past the upstream O2 sensor and mimics a lean condition. One owner found a snapped exhaust manifold bolt during routine inspection.
Reported in 1 NHTSA complaint - 4
Vacuum leak at intake boots, PCV hoses, or brake booster line
Low severityCracked, loose, or perished rubber connections ahead of the MAF let in air the PCM cannot measure, driving the fuel trim lean.
Common cause - 5
Stuck-open PCV valve
Low severityA PCV valve stuck open admits excess, unmetered air into the intake, producing a lean bank-1 condition especially at idle.
Common causeParts:PCV valve - 6
Weak fuel pump or clogged fuel filter
Medium severityReduced fuel delivery pressure under load can't keep pace with airflow, causing the system to run lean; check fuel pressure at idle and under load against spec.
Common cause - 7
Aging or failing upstream oxygen sensor
Low severityA slow or degraded front O2 sensor can report an inaccurate lean signal even when the air-fuel mixture is correct.
Common causeParts:oxygen sensor
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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.
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