P0174 on Mercury
System Too Lean (Bank 2)
P0174 on Mercury vehicles indicates system too lean (bank 2). Au7o has documented this code across 1 Mercury model — most commonly on Sable. 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 Mercury range from $50 to $350, 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 Mercury by Model
Mercury Sable(1 issue)
- Lean-Condition Codes (P0171/P0174), Rough Idle and Stalling1996-2005
Sable V6s commonly set P0171 and P0174 (system too lean, both banks) together, with rough idle, surging, and stalling. Because both banks read lean, the usual culprits are a dirty/failing mass airflow (MAF) sensor, vacuum leaks, PCV system leaks, or weak fuel delivery. A frequently cited Sable-specific cause is the cam-cover-to-intake vent (PCV) tubes: the plastic angle adapters that join the tubes to the cam covers rot out underneath the bend, creating an unmetered air leak. EGR gasket/valve leaks can also contribute.
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View P0174 across all makes →Frequently Asked Questions
What does P0174 mean on Mercury?▼
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 Mercury specifically, this code is documented across 1 model.
What causes P0174 on Mercury vehicles?▼
Common causes on Mercury: 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 Mercury?▼
Repair costs on Mercury range from $50 to $350, depending on the specific model and root cause.
Which Mercury models have P0174 documented?▼
Au7o has documented P0174 on 1 Mercury model: Sable.