The BMW 1 Series, specifically the 128i and 135i models in Coupe and Convertible body styles for the 2009 model year in the USDM, represents a compact premium sports vehicle. Engineered with BMW's renowned driving dynamics and a focus on performance, these models offer an engaging driving experience. The 128i is powered by a 3.0L naturally aspirated inline-6 engine, while the 135i features a more potent 3.0L twin-turbocharged inline-6. Both models are available with a 6-speed manual or 6-speed Steptronic automatic transmission, emphasizing their sporty character and appeal to driving enthusiasts.

This manual provides comprehensive guidance for owners and technicians on the operation, maintenance, and basic troubleshooting of the 2009 BMW 1 Series 128i and 135i Coupe and Convertible models. It covers essential systems including the powertrain, transmission, chassis, electrical components, and the iDrive infotainment system. Key areas addressed include routine maintenance procedures, driver assistance features, safety systems, and instrumentations. While offering detailed information for user-level understanding and basic upkeep, complex repairs are noted to require a dedicated service manual.