Regenerative Braking
Regenerative braking takes some of the energy from the moving vehicle and turns it into electrical energy. This energy is then used to charge the vehicle's hybrid battery system, which increases fuel efficiency.
The torque converter stays locked allowing the drive motor to be coupled to the wheels (through engine and trans) to recharge the hybrid batteries via regenerative braking.
The system works whenever you take your foot off the accelerator pedal while the vehicle is moving in a forward gear. This causes the vehicle to slow down more quickly. It may feel like the brake pedal is being pressed, even when it is not. When the brake pedal is depressed the system will deliver a higher percent of regenerative energy to the hybrid battery system than when in coast down.