So... Start with the TR switch and test it for power.
With the key held in start position and the transmission set at D either H or B will be +12 V ... That one is your input.
Then put it in P or N and the other one should get +12 V.
Remember, you don't have to disconnect anything... Just probe the back of the TR switch connector.
The wire that goes to +12 V only in Park or Neutral is the wire you want to splice. (either H or B... With the key held to start)
With the key held in start position and the transmission set at D either H or B will be +12 V ... That one is your input.
Then put it in P or N and the other one should get +12 V.
Remember, you don't have to disconnect anything... Just probe the back of the TR switch connector.
The wire that goes to +12 V only in Park or Neutral is the wire you want to splice. (either H or B... With the key held to start)