block heater to trigger rs?

2003 Dodge Ram Cummins Diesel

DEI 561-R remote start system.

There is no wts wire on these trucks.  I have read or heard that the wts can be triggered off of the block heater itself.

How can I do this?  Just hook up the wts wire based on the polarity that I see from the block heater?

Is it really that simple?

My wts light is only on for maybe 3 seconds.  The system currently waits 15 sec before it starts.

These trucks don't have glow plugs, they have a heater grid.  It has a big honking wire going to it right at the intake.  I would like to attach the wts trigger wire here and as soon as the heater goes off, have the truck start.

I put this same system on an 01 Dodge diesel but it had the actual wts wire I was able to tap into.  These new trucks use a bus from the pcm.