Tilt Steering Column

BTSI Description

The brake transmission interlock (BTSI) system prevents the automatic transmission from being shifted out of PARK unless the brake pedal is depressed. When the brake pedal is depressed, the BTSI solenoid releases a lock pawl. This enables the shift Linkage to move and the shift lever to operate.
When service operations are required, the BTSI system can be overridden.
On vehicles that are equipped with a column-mounted shift lever, this is done by turning the ignition switch to the OFF position and removing battery voltage from the solenoid.
For vehicles equipped with floor-mounted shift levers, an override lever is mounted on the right side of the assembly. The override lever may be accessed by removing the shift lever boot. Push the lever to the left in order to override the BTSI.

BTSI Circuit Description

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.