gm mechanical p/n safety switch

The DEI Installation manuals have extensive coverage regarding incorporating Neutral Safety Switch shutdown in GM's not equipped with a wired P/N switch. The common strategy utilizes a relay and the key-in-ignition switch contacts.

The downside is of course if you insert the key with the door open, a shutdown is triggered.

Many non-electronic transmission EFI GM's from ~1985 through 1993 (trucks) and 1994(passenger)with column-shift automatics have a switch on the column for back up lights and a P/N signal to the ECM. The ECM circuit is orn/blk(signal) and blk/wht (logic ground). The orn/blk is at GND potential in Park or Neutral. In other gears it is at a logic high ~5.0Volts.

IMO, it would be easier and 'better'(no unwanted shutdown by inserting key) to connect the DEI gry/blk P/N Shutdown to this circuit than the strategies suggested in the manuals. Has anyone ever tried this, or have any comments as to why it should or should not work?

Thanks.

I have never looked for or tested that wire, but the first thing to do would be to make sure that not only is it a ground in park/neutral, but that the ground stays there when the ignition is switched off.

If the ground goes away with the car off, connecting the DEI BLACK/ white neutral safety wire to it would still not allow the remote starter to ever come on, since the ground would be missing.

If that's the case, it might be possible to even rewire the factory switch so that it does what you want, if you can be sure that doing so won't negatively affect operation of the car itself.