P174F on Audi
Fuel Trim Cylinder Balance Bank 2
P174F on Audi vehicles indicates fuel trim cylinder balance bank 2. Au7o has documented this code across 4 Audi models — most commonly on A3, A5, R8. This is a manufacturer-specific fuel-system code (used by some makes, notably BMW) indicating a fuel trim cylinder balance problem on Bank 2 — the bank of cylinders that does not contain cylinder 1. The engine computer compares how much fuel correction each cylinder needs and sets this code when one or more cylinders on Bank 2 run noticeably richer or leaner than the others, creating an air/fuel imbalance. It generally points to something disturbing fueling or air on individual cylinders rather than the whole bank. Symptoms can include rough idle, slight misfire feel, and reduced smoothness. Typical repair costs on Audi range from $500 to $8,000, depending on the specific model and root cause.
Common Causes of P174F
- •Dirty, clogged, or leaking fuel injector on a Bank 2 cylinder
- •Intake or vacuum leak affecting individual cylinders
- •Weak or fouled spark plug / ignition coil causing imbalance
- •Low or uneven fuel pressure
- •Faulty oxygen/air-fuel sensor on Bank 2
- •Carbon buildup on intake valves (direct-injection engines)
- •Compression or valve issue on a Bank 2 cylinder
P174F on Audi by Model
Audi A3(1 issue)
- DQ381/DQ250 S tronic Mechatronic or Internal Transmission Fault Causing No-Drive, Jerking, or Gearbox Warning2016-2024
Multiple A3/S3 owners report sudden gearbox malfunction warnings, harsh shifting, loss of drive, or the transmission becoming stuck in gear. On MQB-based A3 models with dual-clutch gearboxes, failures are commonly traced to the mechatronic unit, internal speed sensors, clutch adaptation faults, or internal transmission hardware. Audi/NHTSA documentation also shows recalls on certain newer A3/S3 vehicles for transmission-related defects that can lead to loss of motive power.
Audi A5(1 issue)
- S-Tronic/DSG Mechatronic Unit Failure2008-2017
The 7-speed S-Tronic (DL501) dual-clutch transmission in the A5 suffers from mechatronic unit failures. The mechatronic unit is the electro-hydraulic control module that manages gear selection and clutch engagement. Internal solenoid and valve body wear causes erratic shifting, shuddering, and eventual loss of gears.
Audi R8(1 issue)
- S-tronic Transmission Actuator Failure2008-2024
The R8 S-tronic dual-clutch transmission uses hydraulic actuators for gear selection and clutch engagement. Actuator failures cause gear selection errors, failed shifts, and transmission lockouts.
Audi S3(2 issues)
- DQ250 DSG Mechatronic Unit Failure2015-2024
The S3 7-speed DSG transmission can develop mechatronic unit faults causing harsh shifts, gear selection errors, and transmission warnings. Solenoid wear and valve body contamination are common root causes.
- DQ381 S-Tronic Mechatronic Unit Failure2015-2024
The Audi S3 (2015-2024) with the 7-speed DQ381 S-Tronic dual-clutch transmission experiences mechatronic unit failures that cause harsh shifting, limp mode, and complete loss of drive. The mechatronic unit (the transmission's electronic brain) contains clutch position sensors, solenoids, and the transmission control unit (TCU). The clutch position sensors (P1735/P1736 faults) are the most common failure point, preventing accurate detection of clutch engagement. Failures typically manifest as loss of odd or even gears, forcing the transmission into safe mode with restricted RPM and gear availability. The DQ381 inherited many weak points from earlier DSG designs. Eco-Torque and Audizine forums report growing numbers of DQ381 mechatronic failures, particularly on S3 models subjected to spirited driving. A new mechatronic unit costs $1,800-$3,000 plus coding and installation. Clutch pack failures add $2,000-$4,000.
Looking for P174F on a different make?
View P174F across all makes →Frequently Asked Questions
What does P174F mean on Audi?▼
P174F stands for "Fuel Trim Cylinder Balance Bank 2." This is a manufacturer-specific fuel-system code (used by some makes, notably BMW) indicating a fuel trim cylinder balance problem on Bank 2 — the bank of cylinders that does not contain cylinder 1. The engine computer compares how much fuel correction each cylinder needs and sets this code when one or more cylinders on Bank 2 run noticeably richer or leaner than the others, creating an air/fuel imbalance. It generally points to something disturbing fueling or air on individual cylinders rather than the whole bank. Symptoms can include rough idle, slight misfire feel, and reduced smoothness. On Audi specifically, this code is documented across 4 models.
What causes P174F on Audi vehicles?▼
Common causes on Audi: Dirty, clogged, or leaking fuel injector on a Bank 2 cylinder, Intake or vacuum leak affecting individual cylinders, Weak or fouled spark plug / ignition coil causing imbalance, Low or uneven fuel pressure, Faulty oxygen/air-fuel sensor on Bank 2. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P174F on a Audi?▼
Repair costs on Audi range from $500 to $8,000, depending on the specific model and root cause.
Which Audi models have P174F documented?▼
Au7o has documented P174F on 4 Audi models: A3, A5, R8, S3.