The A4, produced for the 2003 model year, represents a sophisticated compact executive sedan and wagon built on the Volkswagen Group B6 platform. This generation of the A4 is characterized by its refined styling, high-quality interior materials, and advanced engineering, aiming to compete with premium brands like BMW and Mercedes-Benz. Notable features include the availability of the renowned quattro all-wheel drive system, delivering exceptional traction and driving dynamics, along with a strong emphasis on safety, evidenced by excellent crash test ratings. The A4 offers a range of powertrain options, including turbocharged and naturally aspirated inline-four and V6 engines, all designed to provide a balance of performance and efficiency for discerning drivers. This comprehensive manual serves as a factory service and repair guide for the 2003 A4 (B6 chassis code). It provides extensive coverage, equivalent to over 1000 printed pages, detailing every aspect of the vehicle's maintenance, diagnosis, and repair. Key areas covered include in-depth procedures for engine mechanical and electrical systems, transmissions (both manual and automatic), drivetrain components, suspension, brakes, steering, body and chassis, and the complete electrical system. Additionally, the manual offers detailed information on climate control, safety systems, and infotainment electronics. Owners, mechanics, and technicians will find invaluable guidance for routine maintenance, troubleshooting complex issues, performing component-level repairs, and understanding technical specifications, ensuring the longevity and optimal performance of their A4.