P0174 on Buick
System Too Lean (Bank 2)
P0174 on Buick vehicles indicates system too lean (bank 2). Au7o has documented this code across 2 Buick models — most commonly on Enclave, Encore. P0174 means the engine computer detected that the air-fuel mixture on Bank 2 (the side of the engine with cylinder 2) is running too lean — too much air relative to fuel. The computer monitors this through the oxygen/air-fuel sensors and fuel trims; when it has to add a large amount of extra fuel to compensate and still can't reach the target, it flags the mixture as too lean. A lean condition can cause rough idle, hesitation, or misfires, and over time can raise combustion temperatures. Because it's Bank 2 specific, an unmetered air leak on that bank or a fuel delivery shortfall is typical.
Common Causes of P0174
- •Vacuum or intake air leak (hoses, gaskets, PCV)
- •Dirty or failing mass airflow (MAF) sensor
- •Weak fuel pump or restricted fuel filter (low fuel pressure)
- •Clogged or underperforming fuel injectors
- •Leaking intake manifold or throttle body gasket
- •Faulty or contaminated oxygen / air-fuel sensor
- •Exhaust leak upstream of the oxygen sensor
- •Stuck-open EGR valve
P0174 on Buick by Model
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(1 issue)
- 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.
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View P0174 across all makes →Frequently Asked Questions
What does P0174 mean on Buick?▼
P0174 stands for "System Too Lean (Bank 2)." P0174 means the engine computer detected that the air-fuel mixture on Bank 2 (the side of the engine with cylinder 2) is running too lean — too much air relative to fuel. The computer monitors this through the oxygen/air-fuel sensors and fuel trims; when it has to add a large amount of extra fuel to compensate and still can't reach the target, it flags the mixture as too lean. A lean condition can cause rough idle, hesitation, or misfires, and over time can raise combustion temperatures. Because it's Bank 2 specific, an unmetered air leak on that bank or a fuel delivery shortfall is typical. On Buick specifically, this code is documented across 2 models.
What causes P0174 on Buick vehicles?▼
Common causes on Buick: Vacuum or intake air leak (hoses, gaskets, PCV), Dirty or failing mass airflow (MAF) sensor, Weak fuel pump or restricted fuel filter (low fuel pressure), Clogged or underperforming fuel injectors, Leaking intake manifold or throttle body gasket. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0174 on a Buick?▼
Repair costs vary widely depending on the root cause and specific Buick model.
Which Buick models have P0174 documented?▼
Au7o has documented P0174 on 2 Buick models: Enclave, Encore.