The brake transmission shift interlock (BTSI) system prevents the automatic transmission from being shifted out of the PARK position unless the following conditions are present:
| • | The brake pedal is depressed. |
| • | The ignition switch is turned to the RUN or the START position. |
When the ignition switch is in the RUN or the START position, the current flows from the B/U LPS fuse located in the underhood fuse block through CKT 839 (PNK) to the park/neutral position switch. The park/neutral position switch also feeds the backup lamps portion of the switch. With the transmission in the PARK position, the current flows to the BTSI fuse located in the underhood fuse block through CKT 275 (LT GRN). The current then flows to the stoplamp switch through CKT 584 (LT GRN/BLK). The current continues to the BTSI solenoid through CKT 1135 (DK GRN/WHT). The ground path is provided through CKT 1850 (BLK) to G200 and G201. When the brake pedal is depressed, the normally closed contacts in the stoplamp switch open and the current flow is interrupted. When the current flow is interrupted, the BTSI solenoid de-energizes. The transmission may then shift to another gear. When the transmission shifts to another gear (except PARK), the contacts in the park/neutral switch open. This condition stops the current flow to energize the solenoid when the brake pedal releases.
