P0174 on Audi
System Too Lean (Bank 2)
P0174 on Audi vehicles indicates system too lean (bank 2). Au7o has documented this code across 2 Audi models — most commonly on Q5, SQ5. 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 Audi by Model
Audi Q5(1 issue)
- 2009-2025 Q5 Gasoline-Quality Deposit Diagnosis - TSB 2014753/132009-2025
Audi states that contaminated gasoline or gasoline with insufficient deposit-control additives can contribute to deposits on intake valves, the intake manifold, fuel injectors and combustion chambers. Possible results include rough running after cold start, extended cranking, hesitation, rough idle, reduced performance, poor fuel economy or an MIL with misfire, lean-system or air/fuel-ratio-imbalance faults. This does not establish a universal Q5 intake-valve defect, a mandatory walnut-blasting interval or a fixed failure mileage.
Audi SQ5(1 issue)
- Fuel-Quality or Deposit-Related Rough Running and Misfire Diagnosis2014-2025
Audi states that contaminated gasoline or gasoline with insufficient deposit-control additives can contribute to deposits in injectors, combustion chambers, the intake manifold and intake valves, with rough running, hesitation, reduced performance, poor fuel economy or related ECM faults. This does not establish a universal SQ5 intake-valve defect, a mandatory walnut-blasting interval or a fixed mileage. Audi separately warns that unapproved fuel additives are not permitted on 2018-2025 EA839 V6 TFSI SQ5 models because a negative effect on engine life cannot be ruled out.
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View P0174 across all makes →Frequently Asked Questions
What does P0174 mean on Audi?▼
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 Audi specifically, this code is documented across 2 models.
What causes P0174 on Audi vehicles?▼
Common causes on Audi: 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 Audi?▼
Repair costs vary widely depending on the root cause and specific Audi model.
Which Audi models have P0174 documented?▼
Au7o has documented P0174 on 2 Audi models: Q5, SQ5.