05 tahoe keyless integration remote start

I am installing a Crimestopper RS00-G4 on a 2005 Chevrolet Tahoe Z71 trim. The RS has a three pulse negative input to trigger the starter. The vehicle has working keyless entry, power, etc. In all the instructions I've found for the Tahoe, it says to use the lock motor wire (gray) located in the driver door for this input. I metered the connection and it seems to be positive at rest. Maybe my meter is too slow or the pulse is too fast for me to read on the screen. Is this the right wire to use or is there another one to use? I've ran that wire and the alarm disarm wire into the door already but don't want to try anything until I'm sure about the connection. I have the IB-GMBP bypass for hook up later. Thank you.

lock motor wires are reversed polarity and if you are going to use them you will need to build a relay to trigger from 12 volts to ground.

In that vehicle you need to use a data module, Flash Logic FLDL1 or FLCAN or equivalent. Or you need to run 3 wires into the drivers door and solder them to the circuit board of the lock/unlock switch.

Thank you, I just don't know why my google fu wasn't strong enough. It's such a popular vehicle and I found people claiming to integrate the factory keyless or at least purchasing a unit but, no one doing a tutorial or having problems. I'm going to solve it with a new bypass/data module that will also give me heated accessories. May as well use the BCM data for something worthwhile during starts.