This was very unexpected but i installed a b&m shift plus on my cavalier today and tried starting the car after, and it wont start. wont crank. Just the check engine light still on when the key is turned all the way over. I know i installed it the correct way because i double checked everything to make sure. Undid all the wiring and plugged the trans connector back in and wont start with that either.. so.... any help??

The only thing I can think of is to get the code checked. Run the diagnostic test which you'll need a tester for. And see what code it's throwing, then you can pin point your problem. Sounds electrical.

Did you disconnect the battery while doing the install? If not, try disconnecting it to reset the computer and then reconnect it, checking that everything is tighten up and corrosion free.