trigger door locks from the control unit

This may sound dumb but has anyone here actually opened up their door lock control units and tapped into the circuit board in order to use the alarms negative door lock wires.

I've seen this done 3 times....  once on a nissan skyline gtr 2000 model....  2nd car was a nissan silvia 2002 and third car was a 2000 model lexus.

The installer that managed to do this didnt tell me how the hell he did it..

Does anyone know how he tracked down the right module to tap into?  and how do you trace down which circuit on the board to attach the negative door lock wires too?

Im just asking in general.

I searched the forums and the is no threads on how to do this.

You probably won't find an answer to a Q that basically gets you around the proper way of doing it. That said, i have done this a few times and the only real answer is to go directly to the switch on the door. Any system that would require simple pulses would have wires on the switch, so that leaves those types out of the equation. Since you want to get around resisted value pulses or data, these switches should mostly be mounted to a board with soldier connections. The ones i remember the most are the Ford Probe, Jeep Grand Cherokee, and the new body GM trucks.

In the old Ford Probes, it was simply a matter of opening up the switch and soldiering wires onto the board before the resistors. The Probe had a negative input to the switch and pulses out, which then went thru resistors and then diodes before going together to a single wire(all inside the switch itself). That single wire travelled to the relays in the car. I used to simply open up the switch and soldier to the points where the pulses left the rocker itself, thus creating a negative pulse lock system. Reality is, it's easier to add a couple relays and resisitors in the car then go thru all that. The only reason i ever went thru it was to satisfy a dealer when i was on the road and didn't have what i needed at the time.

On the Cherokee and new GM trucks, it is basically the same way except after the switch the pulses are converted to data. I remember when the new GM's came out in 2007, there were no modules(same with the Cherokee) and the only other choice was to add a bizillion relays to make it all work plus running wires practically everywhere. Now, the amount of time it takes to do all that is way over the cost of a lock module...

Thanks Mike and Howie for sharing some great info....   I like learning new things but some installers dont like sharing their secrets....

On the contrare mon frere we love to share around here,   Even our deepest secrets, you have to ask the right questions,