2 step unlock feature

On a 2001 Malibu the  lock signal is (-) and the unlock signal is (-) as well, but the wiring sheet notes that this signal must pass through a 1.5k res.  Additionally I am using a 2 step unlock feature using a relay.  In detail

the 1st unlock pulse at  #86 triggers the step 1 unlock for the driver side motor from #30 and the next pulse triggers the OEM relay to unlock all doors. 

Now the problem why is this resistor needed since the OEM relay is really doing the switching to look all doors and unlock all doors on the second pulse.  If it is needed is this placed in the 1st step unlock signal, the 2nd step signal to the OEM relay or both. 

Another related post for a 2001 malibu said that the signal is shunted to ground throuh the 1.5k res?  is this correct?

Ok now I understand what this means,  the lock/unlock signal from my module may not be negative in terms of 0 potential, but could throw ground, but in either case I need a resistor (1.5K) in series for the unlock signal.

Is that correct?

By the way, thanks!

On a side not though, this still does not explain why the relay is needed assuming that I were to use only a 1 STEP UNLOCK

From the wiring diagram:

[2] Lock requires a negative trigger, and unlock requires a negative trigger through a 1,500 ohm resistor. Must use relays.

In this situation what are the relays for (under a 1 STEP unlock scheme). 

From your explination its seems that the resistor is only used to make the unlock (-) signal less negative than the lock  (-) signal, and the resistor is attached in series.  where is the relay from the diagram note intended to be placed