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It's complicated to explain but if you understand how the door switches operate and then follow the current flow it all makes sense. The OEM system doesn't use relays and either door switch locks or unlocks both doors at the same time.
Posted schematics are two ways to add remote power door locks. One of them (Viper Responder 350) has built in relays and the other (Viper Model 412V) requires the addition of your own relays. The two wires to find and cut are the lt blue and black wires. These two wires travel between both door lock switches. Best place to find them is by removing the glove box and searching the harness wires in that area. Once you find the correct lt blue and black wires cut them and splice in the circuits as shown in the following two schematics.
As you can see in the schematic diagrams it's easier to wire in a power door lock system if it has "built in" relays. Unfortunately this type of system usually has additional wiring for an alarm system.
Also please note that your model #3108 may have different pinouts but you get the idea. You mention that you already know how to wire it in so this reply is also meant to help others that might want to add remote power door locks as a convenience.
One other owner who uses the external 5-pin relay method wired it a different way with the same results. You cut the 2 black ground wires that are at the passenger door lock switch and reroute them back out the door then wire the 2 relays to them as shown in the following schematic. This takes place behind the glove box as well.
The two wires highlighted in yellow are the 2 wires that previously went to ground at the passenger door lock switch.
Here is the door lock circuit schematic that was deleted in the first post. Second picture has the pin assignments of the door lock switches identified.
