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 LeSabre, Park Avenue. 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. Typical repair costs on Buick range from $400 to $1,200, depending on the specific model and root cause.
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 LeSabre(1 issue)
- LeSabre 3800 V6 Lower Intake Manifold (LIM) Gasket Leak1995-2005
Same 3800 V6 LIM-gasket failure mode as Park Avenue — extremely widespread in 1995-2005 LeSabres. Coolant migrates past degraded plastic-and-rubber gasket into the valley, contaminating engine oil. Owners commonly first notice low coolant with no visible leak; by the time milky oil appears, bearings may already be damaged.
Buick Park Avenue(1 issue)
- Park Avenue 3800 V6 Lower Intake Manifold (LIM) Gasket Leak1995-2005
The 3800 Series II (and early III) V6 in Park Avenue, LeSabre, Riviera, Regal, Lucerne — and shared Pontiac Bonneville/Grand Prix, Olds 88/LSS, Chevy Monte Carlo/Impala — suffers infamous lower intake manifold gasket failure. Plastic intake material softens under coolant exposure (especially Dex-Cool); gasket erodes and leaks coolant into the lifter valley, mixing with oil. Catastrophic if undetected.
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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 on Buick range from $400 to $1,200, depending on the specific model and root cause.
Which Buick models have P0174 documented?▼
Au7o has documented P0174 on 2 Buick models: LeSabre, Park Avenue.