Help wiring Park/Neutral Switch. I'm Baffled!
 

I have a standalone harness for a 2002 GM that has the 2 separate plugs. In the standalone I have 4 wires coming out for it.

Green = Backup Lights
Green = Hot in Park only
Yellow = ?
Purple = ?

I have tried everything I know to wire these through a relay to the starter solenoid off of the ignition switch and can't get it to work. The yellow and Purple have continuity through them in P/N, but must not be grounded because they won't fire the relay. What am I doing wrong here? I have always just found one that was grounded in P/N and used it to fire the 85 on the relay. Thanks guys!

What kind of harness is it? If it's a modded factory one, then you need to hook the yellow wire to 85 of the relay and ground 86. Then hook the purple white wire to the ignition switch, hot in crank only. That sends power during cranking down the ppl/wt wire to the NSS, then from there power goes down the yellow wire to the relay. The other side of the relay will need constant power on one side and to the starter solenoid on the other.

You are a freaking genius LS1! You helped me a year or so ago on a cruise control problem with LED light installed and nailed it. That explains why there is continuity through the purple and yellow when in Park/Neutral. What would the second green wire be that is only hot in Park? Thank you so much for chiming in. This is a '69 Chevy truck over a Duramax chassis and drivetrain.

I don't know about that genius comment, but I've been doing these things for a minute! LOL!

The second green wire I believe is for the shift interlock.

Truck sounds cool, I have a friend who has a "72 on a Duramax chassis. Do you have a build thread anywhere?

LS1, one more question for you. On the stock 2002 Duramax chassis gas tank I have one orange and one purple wire coming off of the sending unit. I have the Dakota Digital gauges that are programmable, but they need to read the ohms from the sending unit. It appears the orange wire is a low reference wire feeding the sending unit from the PCM and the purple wire from the sending unit goes back to the PCM with the PCM telling the gauge what to read. I am not getting an ohm reading through it at all. How would I wire this thing to function? Any ideas? Also, I have no idea how the sending unit grounds in a plastic tank. No wires coming off it at all to ground. Any ideas what may be going on there and what is needed? If continuity is going through them could I just tie them together to the gauge? Thanks!

According to that schematic, you should be getting between 40 and 250ohms when you measure between those two wires. If you're not getting anything, meaning open circuit, it sounds like the sender is bad.

Thanks LS1. I finally figured out last night that the term "low reference" on these schematics means ground. I didn't know that. The light bulb finally came on again! I appreciate your help once again. Lol...