GM Repair Questions? Ask a Mechanic for Answers ASAP
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This problem can be caused by a faulty circuit or BTSI solenoid (brake transmission system interlock) This will be a small solenoid at the shift linkage in console,
It is a pretty good job on this paerticular vehicle. here is info to help you.
Automatic Transmission Shift Lock Control Actuator Replacement
Important: After assembling the shift lock actuator, turn the ignition forward but do not start (auxiliary position) and attempt to pull the lever from PARK with and without the brake pedal depressed to verify there is no gear access without the brake pedal depressed.
Important: Ensure the key cannot be removed from the ignition unless both the shiftier is in PARK and the shift knob button has been depressed.
Tighten Tighten the actuator screw to 1.65 N·m (15 lb in).