Power Door Lock Wiring

I have a 96 jimmy that i am installing an aftermarket keyless entry into. My jimmy has the TRW keyless entry unit under the drivers side kick panel and i know that the light blue and white wires connected to this unit are the power wires for lock and unlock. The problem is i need the negative wires for the negative side of these circuits to hook up the aftermarket unit im using. None of the wires in the TRW unit test as negative except a black one that locks while testing and unlocks afterward. Where can i find the negative wires for the power door locks? Are there seperate relays? Where are they? Thanks for any help.

You can use a couple of standard relays if you wire them properly.