P0174 on Pontiac
System Too Lean (Bank 2)
P0174 on Pontiac vehicles indicates system too lean (bank 2). Au7o has documented this code across 4 Pontiac models — most commonly on Bonneville, Grand Am, Grand Prix. 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 Pontiac 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 Pontiac by Model
Pontiac Bonneville(1 issue)
- Bonneville 3800 V6 Lower Intake Manifold (LIM) Gasket Failure1995-2005
1995-2005 Bonneville with the 3800 Series II / III V6 (L36 NA or L67 supercharged) suffers the same LIM gasket failure that hit Buick Park Avenue/LeSabre, Olds 88, Chevy Monte Carlo, etc. Plastic intake material softens under coolant exposure (especially Dex-Cool); coolant migrates into the valley and oil. Catastrophic if undetected.
Pontiac Grand Am(1 issue)
- Grand Am 3.4L V6 Upper/Lower Intake Gasket Failure1999-2005
The 3.4L LA1 "3400 SFI" V6 in 1999-2005 Grand Am, Alero, Malibu, Venture, Montana, Aztek, Rendezvous, Impala has a notorious upper/lower intake gasket failure mode similar to the 3800 V6 but with a different gasket part. Coolant leaks externally (under the throttle body area), into the lifter valley, and/or onto the timing cover. Often co-fails with the plastic upper intake plenum cracking.
Pontiac Grand Prix(1 issue)
- Grand Prix 3800 V6 Lower Intake Manifold (LIM) Gasket Failure1997-2008
1997-2008 Grand Prix with the 3800 V6 (NA L36 or supercharged L67) — same LIM gasket failure mode as Bonneville and Buick variants. Particularly common on the supercharged GTP because higher boost pulls coolant past the eroded gasket faster.
Pontiac Montana(1 issue)
- Montana 3.4L V6 Intake Gasket — Same as Grand Am1999-2005
Same 3.4L LA1 V6 upper/lower intake gasket failure as Grand Am. The U-body minivans (Pontiac Montana, Chevy Venture, Olds Silhouette) all share the engine and the failure pattern. Often presents earlier on the minivans due to higher load duty cycles.
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View P0174 across all makes →Frequently Asked Questions
What does P0174 mean on Pontiac?▼
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 Pontiac specifically, this code is documented across 4 models.
What causes P0174 on Pontiac vehicles?▼
Common causes on Pontiac: 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 Pontiac?▼
Repair costs on Pontiac range from $400 to $1,200, depending on the specific model and root cause.
Which Pontiac models have P0174 documented?▼
Au7o has documented P0174 on 4 Pontiac models: Bonneville, Grand Am, Grand Prix, Montana.