Safety Neutral Switch replacement schematic/diagram needed

For the starting section of it power from the back-up fuse comes in on the pink wire on pin1 and in park or neutral it should come out on the orange/black on pin 3 to the PCM. PCM switches the yellow wire to the starter relay to ground to enable the starter. None of the rest of the switch effects starting.
Replacement isn't that hard, remove the battery tray, then put the transmission in neutral and remove the shift lever on the shaft. Bend the locking tab down and remove the nut and washers. Remove the two bolts and the stud and the switch lifts off. Reverse the process to install the new one, leave the bolts a bit loose for adjustment. To adjust it to position they want you to have a special tool but it isn't that hard to do it without the tool if you look at how the tool lines up.

Not a mistake but not the correct pin for testing. Both 1 and 4 get voltage from the same source It's just used for different things inside the switch. Shouldn't hurt anything either way. However it would be possible for pin 1 to have power and pin 4 to have a bad connection or pin fit issue that jumping voltage from pin 1 would have masked. I would probably test for voltage on both pins, if you don't have voltage on pin 4 in the connector that is likely the problem and not internal switch failure.

Yes. It should have the same voltage as pin one. They share the same circuit from the same fuse so if you have power on pin 1 but not pin 4 there is a problem in that feed wire. See the attached, both connect at the under hood fuse block in connector C1 terminal A11. Very possible the wire failed at that connection if you have no power at the other end. That voltage goes in to the switch on pin 4 and then should come out on pin 3 when the switch is in park or neutral. However if you don't have voltage on pin 4 of the connector on the harness then that won't function.
It could be right in the connector at the transmission, they get any moisture in them and the wires corrode off. There are a couple tests for that one is a simple tug test, take a grip on the connector and the wire a few inches up and give it a tug, if the wire pulls out and is green on the end you have the answer the other is to use a piercing probe or sharp pin you could poke it through the insulation of the pink wire on pin 4 and see if you find voltage above the connector. That would tell you if it's the connection there or up at the fuse block.
Then it's simple to trace the wire and repair it or just make a quick "temporary" repair by going a few inches up from the connection on the switch and splicing the pink wire that feeds pin 4 to the pink wire that feeds pin one. That is assuming the problem is farther up the wire and not in the connector itself.

Another quick test just to be sure it isn't the switch itself. Take a meter set to ohms and connect it to pin 4 and pin 3 with the shifter in park, it should show a connection in park and neutral and open in other positions. If that is good then it's just the lack of power at pin 4 as covered above. That would pinpoint the problem even more.

A cut wire would cause a problem for sure. Good job finding it. As it has been open a while I would suggest cutting out a section of the wire and replacing it because it will likely start to corrode inside the insulation and then you get the problem again. Or because you know where that wire is now you could seal it with some liquid tape and then a couple wraps of regular electrical tape and just keep it in mind if it acts up again.

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