https://docs.emtronaustralia.com.au/transmission-control/tuning/converter-lockup/index.htmlThe torque converter lockup clutch mechanically joins the engine to the transmission input, bypassing the converter’s fluid coupling. With the clutch locked there is no converter slip: less heat in the transmission oil, better fuel economy, and a direct connection between the throttle and the wheels. With it unlocked the converter can slip and multiply torque, which helps launches and low-speed driving. The TCM decides when the lockup clutch should be locked or unlocked, how much pressure to apply, and how quickly to apply and release it. Each of these can be tuned separately for each phase of operation (takeup, launch, in gear, up shifts and down shifts).Hugoen-us