[fdryer]

The Brake Transmission Shift Interlock (BTSI) is a Park lock mechanism to prevent shifting out of Park position if the brake pedal isn't pressed (you can thank Audi 5000 drivers unable to tell the difference between the brake and gas pedal when cars and trucks never had shifter interlocks activated by brake pedal. They mysteriously accelerated thru garages, crossed the street, drove into backyard pools, etc. The result is the brake interlock mechanism forcing brake pedal application to allow unlocking the shifter. The btsi is electronically sensed and controls a solenoid in the shifter assembly.

Lift the shifter boot cover to reveal the mechanics to the shift lever. You should see a white plastic tab locking the shifter in Park position. Lift, push or pull the tab out of the way to release the shifter from Park position and shift into gear or neutral.

Others here bought used BCMs and didn't have problems with the relearn procedure.