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HOMESERVICE MANUALSBUICK1999REGAL LSREPAIR AND DIAGNOSISTRANSMISSIONAUTOMATIC TRANSSHIFT INTERLOCK SYSTEMSSYMPTOM TESTSSHIFT LOCK CONTROL ALWAYS ON (IGNITION IN ON POSITION)"W" BODY (INTRIGUE)
1999 Buick Regal LS

"W" Body (Intrigue)

1999 Buick Regal LSSECTION "W" Body (Intrigue)
  1. Place gearshift lever in "P" position. Check BTSI fuse (10-amp) for an open. If fuse is blown, go to next step If fuse is okay, go to step  5.
  2. Disconnect BTSI solenoid connector. Using test light, backprobe between BTSI fuse (10-amp) terminal C4 and battery power. See WIRING DIAGRAMS . If test light illuminates, go to next step. If test light does not illuminate, replace BTSI fuse (10-amp), reconnect BTSI solenoid, then go to step  15.
  3. Disconnect brakelight switch 4-pin connector C2. Using test light, backprobe between BTSI fuse (10-amp) terminal "C4" and battery power. If test light does not illuminate, go to next step. If test light illuminates, check for short to ground in circuit between brakelight switch 4-pin connector C2 terminal "A" and BTSI fuse (10-amp) terminal "C4". See Figure. See WIRING DIAGRAMS . Repair as necessary, then go to step  15.
  4. Check for short to ground in circuit between brakelight switch 4-pin connector C2 terminal "B" and BTSI solenoid connector terminal "A". See Figure and Figure . See WIRING DIAGRAMS . Repair as necessary, then go to step  15.
  5. Turn ignition switch to ON position. Using test light, backprobe between brakelight switch 4-pin connector C2 terminal "A" and ground. If test light does not illuminate, go to next step. If test light illuminates, go to step  8.
  6. Using test light, backprobe between BTSI fuse (10-amp) terminal "C3" and ground. See WIRING DIAGRAMS . If test light illuminates, check for poor connection or open circuit between brakelight switch 4-pin connector C2 terminal "A" and BTSI fuse (10-amp) terminal "C4". Repair as necessary, then go to step  15. See Figure. See WIRING DIAGRAMS . If test light does not illuminate, go to next step.
  7. Check for poor connection or open circuit between ignition switch connector C2 terminal "B" and BTSI fuse (10-amp) terminal "C3". See Figure. Repair as necessary, then go to step  15. See Figure. See WIRING DIAGRAMS .
  8. Disconnect brakelight switch 4-pin connector C2. Using test light, backprobe between brakelight switch 4-pin connector C2 terminal "B" and ground. See Figure. If test light illuminates, go to next step. If test light does not illuminate, check brakelight switch adjustment. Adjust as necessary, then go to step  15. If brakelight switch is adjusted correctly, replace brakelight switch, then go to step  15.
  9. Turn ignition switch to OFF position. Disconnect BTSI solenoid connector. Turn ignition switch to ON position. Using test light, backprobe between BTSI solenoid connector terminal "A" and ground. If test light illuminates, go to next step. If test light does not illuminate, repair open circuit between BTSI solenoid connector terminal "A" and brakelight switch 4-pin connector C2 terminal "B", then go to step  15. See Figure and Figure . See WIRING DIAGRAMS .
  10. Using test light, backprobe between BTSI solenoid connector terminal "A" and "B". If test light does not illuminate, go to next step. If test light illuminates, check BTSI solenoid linkage for mechanical damage. Repair as necessary, then go to step  15. If BTSI solenoid linkage is okay, replace BTSI solenoid, then go to step  15.
  11. Turn ignition switch to OFF position. Reconnect BTSI solenoid connector. Using test light, backprobe between underhood junction block 68-pin connector C1 terminal "A12" and battery power. See Figure. If test light illuminates, go to next step. If test light does not illuminate, go to step  13.
  12. Using test light, backprobe between underhood junction block 68-pin connector C2 terminal "C11" and battery power. See Figure. If test light does not illuminate, replace underhood junction block, then go to step  15. If test light illuminates, repair open circuit or poor connection between underhood junction block 68-pin connector C2 terminal "C11" and BTSI solenoid connector terminal "B", then go to step  15. See WIRING DIAGRAMS .
  13. Using test light, backprobe between TR switch connector C1 terminal "A" and battery power. See Figure. If test light does not illuminate, go to next step. If test light illuminates, repair open circuit or poor connection between TR switch connector C1 terminal "A" and underhood junction block connector C1 terminal "A12", then go to step  15. See Figure. See WIRING DIAGRAMS .
  14. Using test light, backprobe between TR switch connector C1 terminal "D" and battery power. See Figure. If test light illuminates, check TR switch adjustment. Adjust TR switch as necessary, then go to next step. If TR switch adjustment is correct, replace TR switch, then go to next step. If test light does not illuminate, repair open circuit or poor connection between TR switch connector C1 terminal "D" and ground (G129) located on transaxle stud, then go to step  15. See WIRING DIAGRAMS .
  15. Ensure all components disconnected or removed during testing are reconnected and installed on vehicle. Ensure BTSI system operates correctly. See SHIFT INTERLOCK SOLENOID  under DESCRIPTION & OPERATION. If system does not operate correctly, repeat step  1.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.