Zac, thanks a lot for your help.

I'm trying to find the diagnostic wire you're talking about. Is it like the other end of the ODBII? Where exactly is it plugged in, and should I just cut the harness tape opena nd find the black wire, and solder my brain-unit violet wire to it?

It's the part circled in red. Says diagnosis on top. Take apart the tape on the wires going into it and find the black wire. And yes just cut off off some of the coating of the black wire and solder the tach wire from the brain to it, I think it should be a violet/white wire.

Ok so I pulled the brain out, and got the exact model number: 4103XV.

I got the installation guide for that unit. I found the violet/wire that is the tach. input.

I also found the diagnostic wire (obviously and clearly marked).

So from the manual, there are 3 methods registering if the vehicle is running that the remote start can use.

1) Voltage
2) Simulated tach-voltage option
3) Tach.

Then there were two options for setup, 1) just leave it how it is. 2) Use the program button to use learn the tach.

So I followed this procedure to have it learn the tach. I can't tell if the tach is even hooked up, but I went ahead and did the procedure, and it blinked successfully.

So I may have switched something other, but I can't telll until it's actually cold enough to see find out.

I tested it in currenty conditons, and it works great.

So if it's cold and wont start up, then I'll go through the procedure of hooking violet-white wire through firewall to black wire in diagnostic wire (tach signal).

Thanks for your guys help.

the tach will work fine in cold weather. it will keep cranking until it starts.