Shift Interlock System: Other GMC Sonoma II

BRAKE TRANSMISSION INTERLOCK SOLENOID

Note. Brake Transmission Shift Interlock (BTSI) solenoid may also be known as shift interlock actuator.

Gear selector cannot be moved from Park without depressing brake pedal if ignition is on. When pressure is applied to brake pedal, BTSI solenoid is de-energized to release gear selector from Park. Brakelight switch interrupts circuit to mechanically unlock gear selector by de-energizing BTSI solenoid. See WIRING DIAGRAMS .

PARK LOCK CABLE

Gear selector is locked in Park when ignition switch is in LOCK position. With ignition on, gear selector is allowed movement to desired position. Ignition key cannot be removed until gear selector is returned to Park. Park lock cable is located on steering column. (Scheme 6)

Scheme 6

BTSI CONTROL INOPERATIVE

Note. Ensure Park/Neutral Position (PNP) switch is adjusted properly. See appropriate AUTOMATIC TRANSMISSION SERVICING article in TRANSMISSION SERVICING. Verify system operation after performing any repairs. See SYSTEM OPERATION CHECK under TROUBLE SHOOTING.

"C", "G" & "K" Series (Except Sierra & Silverado)

1. Disconnect BTSI solenoid harness connector. Measure voltage between battery positive terminal and ground circuit (Black wire) at BTSI solenoid harness connector. If battery voltage is present, go to step 3 . If battery voltage is not present, go to next step.
2. Repair open in ground circuit (Black wire) between BTSI solenoid and chassis ground.
3. Place gear selector in Park. Turn ignition on. Measure voltage between ground and ignition feed circuit (Dark Green/White wire) at BTSI solenoid harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 5 .
4. Adjust or replace BTSI solenoid.
5. Disconnect brakelight switch harness connector. Check for continuity in ignition feed circuit (Dark Green/White wire) between brakelight switch circuit and BTSI solenoid. If continuity is present, go to step 7 . If continuity is not present, go to next step.
6. Repair open in ignition feed circuit (Dark Green/White wire) between brakelight switch and BTSI solenoid.
7. Measure voltage between ground and ignition feed circuit (Light Green wire) at brakelight switch harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 9 .
8. Replace brakelight switch.
9. Disconnect PNP switch harness connector. Check for continuity in ignition feed circuit (Light Green wire) between PNP switch and brakelight switch. If continuity is present, go to step 11 . If continuity is not present, go to next step.
10. Repair open in ignition feed circuit (Light Green wire) between PNP switch and brakelight switch.
11. Measure voltage between ground and ignition feed circuit (Pink wire) at PNP switch harness connector. If battery voltage is present, go to step 13 . If battery voltage is not present, go to next step.
12. Repair open in ignition feed circuit (Pink wire) between PNP switch and TURN/BU (20-amp) fuse located in instrument panel fuse block.
13. Adjust or replace PNP switch.

Sierra, Silverado, & "S" & "T" Series

Note. BTSI solenoid is integral with automatic transmission controller on "S" & "T" series utility vehicles equipped with floor shifter.

1. Set parking brake. Turn ignition on. Place gear selector in Reverse. If back-up lights illuminate, go to step 5 . If back-up lights do not illuminate, go to next step.
2. Check for open in ignition feed circuit (Pink wire) between PNP switch and B/U LPS (25-amp) fuse located in underhood electrical center. If circuit is open, go to next step. If circuit is okay, go to step 4 .
3. Repair open in ignition feed circuit (Pink wire) between PNP switch and B/U LPS (25-amp) fuse.
4. Replace PNP switch.
5. Place gear selector in Park. Using test light connected to ground, probe BTSI (10-amp) fuse located in underhood electrical center. If test light illuminates, go to step 9 . If test light does not illuminate, go to next step.
6. Check for open in ignition feed circuit (Light Green wire) between PNP switch and BTSI (10-amp) fuse. If circuit is open, go to next step. If circuit is okay, go to step 8 .
7. Repair open in ignition feed circuit (Light Green wire) between PNP switch and BTSI (10-amp) fuse.
8. Replace PNP switch.
9. Disconnect brakelight switch harness connector. Using test light connected to ground, probe ignition feed circuit (Light Green/Black wire) at brakelight switch harness connector. Turn ignition on. If test light illuminates, go to next step. If test light does not illuminate, go to step 13 .
10. Reconnect brakelight switch harness connector. Disconnect BTSI solenoid harness connector. Using test light connected to ground, probe ignition feed circuit (Dark Green/White wire) at BTSI solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 14 .
11. Connect test light between BTSI solenoid harness connector terminals. If test light illuminates, go to next step. If test light does not illuminate, go to step 17 .
12. Replace BTSI solenoid.
13. Repair open in ignition feed circuit (Light Green/Black wire) between brakelight switch and BTSI (10-amp) fuse.
14. Turn ignition off. Check for continuity in ignition feed circuit (Dark Green/White wire) between brakelight switch and BTSI solenoid. If continuity is present, go to next step. If continuity is not present, go to step 16 .
15. Replace brakelight switch.
16. Repair open in ignition feed circuit (Dark Green/White wire) between brakelight switch and BTSI solenoid.
17. Repair open in ground circuit (Black wire) between BTSI solenoid and chassis ground.

BTSI CONTROL ALWAYS ON WITH IGNITION ON

Note. Ensure Park/Neutral Position (PNP) switch is adjusted properly. See appropriate AUTOMATIC TRANSMISSION SERVICING article in TRANSMISSION SERVICING. Verify system operation after performing any repairs. See SYSTEM OPERATION CHECK under TROUBLE SHOOTING.

1. Place gear selector in Park. Turn ignition on. Depress brake pedal. Measure voltage (backprobe) between ground and ignition feed circuit (Dark Green/White wire) at brakelight switch harness connector. If battery voltage is present, go to step 3 . If battery voltage is not present, go to next step.
2. Disconnect BTSI solenoid harness connector. Disconnect brakelight switch harness connector. Measure voltage between ground and ignition feed circuit (Dark Green/White wire) at BTSI solenoid harness connector. If battery voltage is present, go to step 5 . If battery voltage is not present, go to step 4 .
3. Replace brakelight switch.
4. Check for mechanical binding. If no problem is found, adjust or replace BTSI solenoid.
5. Repair short to voltage in ignition feed circuit (Dark Green/White wire) between brakelight switch and BTSI solenoid.

Sierra, Silverado, & "S" & "T" Series Pickup

1. Disconnect brakelight switch harness connector. Attempt to move gear selector. If gear selector moves from Park, go to next step. If gear selector does not move from Park, go to step 3 .
2. Replace brakelight switch.
3. Using test light connected to ground, probe ignition feed circuit (Dark Green/White wire) at BTSI solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 5 .
4. Repair short to battery voltage in ignition feed circuit (Dark Green/White wire) between BTSI solenoid and brakelight switch.
5. Check for binding linkage. If linkage is okay, replace BTSI solenoid.

"S" & "T" Series Utility (With Column Shift)

1. Disconnect brakelight switch harness connector. Using ohmmeter, test brakelight switch operation. If brakelight switch operation is okay, go to step 3 . If brakelight switch operation is not okay, go to next step.
2. Replace brakelight switch.
3. Turn ignition on. Using test light connected to ground, probe ignition feed circuit (Dark Green/White wire) at brakelight switch harness connector. If test light illuminates, go to step 5 . If test light does not illuminate, go to next step.
4. Repair short to voltage in ignition feed circuit (Dark Green/White wire) between BTSI solenoid and brakelight switch.
5. Replace BTSI solenoid.

"S" & "T" Series Utility (With Floor Shift)

1. Disconnect brakelight switch harness connector. Using ohmmeter, test brakelight switch operation. If brakelight switch operation is okay, go to step 3 . If brakelight switch operation is not okay, go to next step.
2. Replace brakelight switch.
3. Turn ignition on. Using test light connected to ground, probe ignition feed circuit (Dark Green/White wire) at brakelight switch harness connector. If test light illuminates, go to step 5 . If test light does not illuminate, go to next step.
4. Repair open in park solenoid or park solenoid ignition feed circuit (Dark Green/Black wire) between automatic transmission controller and splice pack.
5. Repair short to voltage in park solenoid or BTSI solenoid ignition feed circuit (Dark Green/Black wire) between automatic transmission controller and brakelight switch.

Note. Brake Transmission Shift Interlock (BTSI) solenoid may also be known as shift interlock actuator. The following adjustment procedure applies to vehicles equipped with column shifter. Adjustment procedure for vehicles equipped with floor shifter is not available from manufacturer.

Actuator is located on steering column. (Scheme 7) Pull locking tab outward from block side of actuator. (Scheme 8) Ensure gear selector is in Neutral. Press on adjuster block to compress internal adjuster spring and engage adjuster teeth. Slide adjuster block as far away from solenoid as possible. Move gear selector into Park. Push locking tab back into adjuster block. Ensure proper operation of system.

Scheme 7

Scheme 8

1. Lift cable lock button. Move gear selector into Park. Snap cable connector into shifter base. Ensure ignition switch is in ON position.
2. Snap cable housing into ignition switch inhibitor. Turn ignition key to LOCK position. Snap cable end onto park lock lever pin. Remove slack from cable connector. Snap cable connector lock button down.