The Brake Transmission Shift Interlock (BTSI) is designed to interrupt shifting when energized. The BTSI is energized whenever the ignition switch is in ON or START and is disabled when the brake pedal is depressed. The BTSI switch receives ignition voltage through the park/neutral position switch only when the transmission shift lever is in the PARK or NEUTRAL position. The park/neutral position switch receives ignition voltage from the BTSI BU MiniFuse® #21 through CKT 341. The BTSI switch is part of the brake switch assembly and is normally closed, providing voltage to the brake transmission shift interlock control solenoid. The BTSI control solenoid gets its ground path through CKT 150. The BTSI control solenoid is energized and prevents the transmission shift lever from being moved out of PARK or NEUTRAL when the ignition switch is in the ON position, the park/neutral position switch is in the PARK or NEUTRAL position, and the brake pedal not depressed. When the brake pedal is depressed, the brake switch opens, removing voltage from the BTSI control solenoid, allowing operation of the shift lever.