P0171 on Buick
System Too Lean (Bank 1)
P0171 on Buick vehicles indicates system too lean (bank 1). Au7o has documented this code across 3 Buick models — most commonly on Cascada, Enclave, Encore. This code means the engine's computer has detected that the air-fuel mixture on Bank 1 (the side of the engine with cylinder #1) is running too lean — meaning there is too much air relative to fuel. The computer watches the oxygen sensors and has had to add a large amount of extra fuel (long-term fuel trim) to try to compensate, but it has hit its correction limit. A lean condition can cause rough idle, hesitation, reduced power, and over time can run the engine hotter than normal. It usually points to either unmetered air leaking into the engine or not enough fuel being delivered.
Common Causes of P0171
- •Vacuum or intake air leak (cracked hose, gasket, or PCV system)
- •Dirty or failing mass airflow (MAF) sensor
- •Weak fuel pump or restricted fuel filter
- •Clogged or dirty fuel injectors
- •Faulty or aged upstream oxygen sensor
- •Leaking intake manifold gasket
- •Low fuel pressure or failing fuel pressure regulator
- •Exhaust leak ahead of the oxygen sensor
P0171 on Buick by Model
Buick Cascada(1 issue)
- PCV Pressure-Regulator Diaphragm Can Crack (Special Coverage N192291620)2016
GM Special Coverage N192291620 identifies selected 2016 Buick Cascada vehicles with the 1.6L engine in which the PCV pressure-regulator diaphragm, built into the engine camshaft cover, may crack. Excess intake air can then cause rough running, especially at idle, illuminate the check-engine light and set P0171 or another airflow-related DTC.
Buick Enclave(1 issue)
- Cold-Weather PCV Deposits Can Cause Reduced Power (PI0746)2008-2011
GM PI0746 covers 2008-2011 Buick Enclave vehicles with the 3.6L LY7 or LLT engine. After a cold start or low-ambient-temperature driving, condensation can freeze at the throttle-body base while engine vapors, fuel dilution and oil mist collect in the air-inlet duct. The condition can illuminate the MIL and cause poor performance or reduced acceleration.
Buick Encore(3 issues)
- EVAP Purge Valve May Not Fully Close (Special Coverage N232395300)2020
GM Special Coverage N232395300 identifies certain 2020 Buick Encore vehicles with the 1.4L LUV engine whose evaporative-emissions purge valve may not fully close. The engine can run rough, hesitate or stall at idle, the check-engine light can illuminate and an EVAP or fuel-trim DTC can set.
- PCV Pressure-Regulator Diaphragm Can Crack (Special Coverage N202299080)2014
GM Special Coverage N202299080 identifies certain 2014 Buick Encore vehicles whose PCV pressure-regulator diaphragm, integrated into the engine camshaft cover, can crack. Excess air can then enter the intake, causing rough running especially at idle, a check-engine light and P0171 or another airflow-related DTC.
- Oil Consumption, Blue Smoke or PCV Faults (PIP5197H)2013-2019
GM PIP5197H covers 2013-2019 Encore vehicles with the 1.4L LUJ/LUV engine. The documented concern includes oil use of at least one quart per 2,000 miles when not caused by an external leak, blue exhaust smoke, a whistle, MIL or fuel-trim codes. Possible causes include a leaking cam-cover PCV orifice, a missing intake-manifold non-return valve or a weak/broken piston ring land.
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View P0171 across all makes →Frequently Asked Questions
What does P0171 mean on Buick?▼
P0171 stands for "System Too Lean (Bank 1)." This code means the engine's computer has detected that the air-fuel mixture on Bank 1 (the side of the engine with cylinder #1) is running too lean — meaning there is too much air relative to fuel. The computer watches the oxygen sensors and has had to add a large amount of extra fuel (long-term fuel trim) to try to compensate, but it has hit its correction limit. A lean condition can cause rough idle, hesitation, reduced power, and over time can run the engine hotter than normal. It usually points to either unmetered air leaking into the engine or not enough fuel being delivered. On Buick specifically, this code is documented across 3 models.
What causes P0171 on Buick vehicles?▼
Common causes on Buick: Vacuum or intake air leak (cracked hose, gasket, or PCV system), Dirty or failing mass airflow (MAF) sensor, Weak fuel pump or restricted fuel filter, Clogged or dirty fuel injectors, Faulty or aged upstream oxygen sensor. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0171 on a Buick?▼
Repair costs vary widely depending on the root cause and specific Buick model.
Which Buick models have P0171 documented?▼
Au7o has documented P0171 on 3 Buick models: Cascada, Enclave, Encore.