How does the Park/Neutral wire function?

Does the ECM expect to see current flowing through it when the car is in park or neutral, and this circuit is broken when the car is shifted into gear?


I'm trying to wire up my aftermarket harness to a B&M Megashifter, and it looks like I should splice the P/N wire into two ends, with either end going to one of the "prongs" on the switch on the shifter.

My car doesn't have a wire in the steering column to splice the P/N wire into as far as I can tell (I think it's a mechanical interlock, which just prevents the key from physically turning to the start position when the linkage isn't in park or neutral), so this seems like the only solution for me.

Is this correct?

 

The park/neutral wire to the ECM: ground it when in park or neutral, open when not. Stick shift cars just leave the wire open, so it is always in drive.

Please note that this wire to the ECM is not the neutral stop safety switch. There is another switch to disable the starter if the shifter is not in neutral or park.

RBob.

 

So would my original idea be correct?
Is the wire properly grounded when the switch on the shifter completes the connection?

(I'm still learning wiring)