sounds like its in the shifter assembly, you could try cleaning the seliniod and putting some wd 40 on the mechanism and see. never had one apart but seems like you could try that first then replace it if it doesnt work
Brake Transmission Shift Interlock Replacement
•Disconnect the negative battery cable. Refer to
Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.
For Vehicles equipped with OnStar® (UE1) with Back Up Battery:
The Back Up Battery is a redundant power supply to allow limited OnStar® functionality in the event of a main vehicle battery power disruption to the VCIM (OnStar®module). Do not disconnect the main vehicle battery or remove the OnStar® fuse with the ignition key in any position other than OFF. Retained accessory power (RAP) should be allowed to time out or be disabled (simply opening the driver door should disable RAP) before disconnecting power. Disconnecting power to the OnStar® module in any way while the ignition is On or with RAP activated may cause activation of the OnStar® Back-Up Battery (BUB) system and will discharge and permanently damage the back-up battery. Once the Back-Up Battery is activated it will stay on until it has completely discharged. The BUB is not rechargeable and once activated the BUB must be replaced.
in Cautions and Notices..
•Remove the lever handle assembly from the shifter.
•Dissassemble the console, as needed, in order to access the shift control assembly. Refer to Console Replacement in Instrument Panel, Gauges, and Console.
•Remove the park lock cable from the shift control assembly.
•Remove the shift control cable from the shift control assembly.
•Disconnect the electrical connectors.
•Remove the shift control assembly.
•Remove the shift interlock solenoid assembly from the control assembly.
1998 Bonneville SSE
2007 Monte Carlo LT-KYB, Clarion, Polk audio, Kicker
1999 Yukon SLE-KYB, Air lift, Reese dual-cam, Tekonsha
1987 Firebird-355/th400-nothing stock