Debuting in late 2004 for the 2005 model year, the second-generation Acura RL (KB1 chassis) introduced Acura's Super Handling All-Wheel Drive (SH-AWD) system, capable of continuous active torque vectoring across the rear axle. The aluminum-intensive body structure utilized carbon-fiber reinforced plastic for the driveshaft. Technological highlights included Adaptive Front-lighting System (AFS) and Active Noise Cancellation (ANC). Engineering priorities for this generation focused on structural rigidity, chassis refinement, and elevating active safety capabilities.

Initial KB1 models featured a 3.5-liter J35A8 V6 engine producing 290 horsepower paired with a 5-speed automatic transmission. The updated KB2 release for the 2009 model year brought a larger 3.7-liter J37A2 V6 engine (300 hp), revised chassis tuning, new Power Plenum exterior styling, and a 6-speed automatic transmission added for 2011. A comprehensive list of standard features combined with proven powertrain durability helped secure a strong market presence in its segment.