If you Altered, Broke or Bypassed/Defeated any Mechanical or Electrical portion of this Park Lock Circuitry Diagram shown in the PDF listed below and the vehicle is now capable of being started while in ANY gear position, then you should repair this problem back to the OEM Safe Condition First ...BEFORE investigating or changing out the The Park Neutral Safety Switch (PNSS) on the Transmission as the source of the problem.
If you destroyed the Shift Lock Solenoid located in the underside of the Center Console...it will have to be replaced.
@MAY03LT has this video to help you disassemble the area enough to gain access to the components and replace what is ordinarily obscured from easy access and view. And even though his reasons doing the R&R relate to different issues from your own ...watch closely for the imagery that shows the location of the Broken/Damaged Lock Solenoid and how to get the Broken A/T Shift Lock Actuator Solenoid Out...and a New One back In:
Click on the "YOUTUBE" Icon at the Lower RH Side to go to Youtube to view this video:
In general, if the Fastener holding on the PNSS has been tightened down hard enough to mushroom the end of the 4L60E Shift Position Armature underneath it… if you don’t remove that burred expansion with a file before installing a brand new Park Neutral Safety… the Internal Rotating Plastic Piece on the inside of the PNSS will be damaged as you try to force it over the Mushroomed End into position.
It may also be necessary to use Needle Nose Pliers to carefully and completely destroy the Two Connection Points where the Electrical Harness Plugs attach inside of the body of the PNSS to get them loose from the Factory applied "Gorilla Glue" that holds the plugs in place. And so great care must be observed so as not to ruin either the Two Harness Plugs... or their Wiring. It is unclear which year your Envoy is...so this is the Best Available PDF on the subject:
“The following schematic describes the 2003 GMC Envoy XL Shift Interlock System Wiring and Circuit Diagram. The shift interlock system is designed to prevent the automatic transmission from being shifted out of PARK to any range unless the brake pedal is depressed. GMC Envoy XL Shift Interlock System consists of fuse (under-hood fuse block), park/neutral position switch, stop lamp switch, A/T shift lock actuator.”
http//
www.justanswer.com/uploads/JHoop/2008-03-03_131052_shift_solenoid.pdf