gmc yukon door locks

 Ook all, I am stumped…I have done a lot of searching on here, and cannot find an answer or a possible thing to troubleshoot.  I am putting a python 581xp in a 94 two door gmc Yukon.  I have everything hooked up and working, except for the lock function on the remote.  I have the locks hooked up for positive pulse using the 5 wire alternating relays.  Here is how I have them pinned out:

Lock relay:

Unlock relay:

Here is the deal:  the unlock function works normally both from the remote and from the switch. The lock function, however, works from the switch and not from the remote.  When I try to lock the vehicle from the remote, the relay does activate, but the lock actuator does not.  I have tried everything that I can think of am I am just stumped.  I cant understand why it is working from the switch but will not work from the relay.  I have tried 4 different relays, all were working.  I am stuck on this. I don’t understand why it wont trigger the locks from the relay, but the unlock works fine.  Hopefully somebody has an idea of what I can try…. Thanks in advance.

-Nate

Are yuo POSITIVE you don't have 87a, and 30 switched?

You sound like you have some skills. unhook both 87a, and 30, and verify the switch side of the wire......

Go to the relays above the gas pedal and test there as well.

funny thing there is, on this yukon, there is not a relay pack above the gas pedal.  i had to hit the wires underneath the speaker.  I just got done doing a bunch more testing.  I took the relays off the wires for the locks, and jumpered them each together so it was just like stock again.  the switch operated fine, and when i manually pulsed the unlock wire to 12v, the doors unlocked just like they are supposed to.  HOWEVER, when i manually pulsed the lock wire to 12v, the wire sparked like it was shorting and the locks did nothing.  so there is obviously a short in the lock wire somewhere.  the weird thing is, if I pulse the lock wire to 12v and it shorts, wouldnt the wire also short when the switch pulses it to 12v, which would cause a fuse to blow?  but no fuse blows, just shorts when i manually pulse it, and works fine if i use the switch.  I am officially stumped.

and thanks, I would like to think i have a couple skills, I have been installing for about 4 years now, mostly on the side. used to work for best buy, and got my mecp cert. then started doin installs for friends and a couple for my buddys shop when his installer is on vaca....

You had the wrong wire for lock. lock is BLACK/ red, unlock is lt.blue. black is constant ground. Get them corrected & try again.

I know one thing for sure, revolutionz_s13 got the ground wire (which is black) mixed up with the BLACK/ red wire. Quess what happen when you pulse +12v to ground ?

weird...apparently no one seems to think that I know how to work a multimeter.  #1.  I am not having any trouble with the UNLOCK function, just the lock function, so obviously I have the right wire.  #2.  the BLACK wire, which rests at ground, UNLOCKS the vehicle when pulsed to 12v.  #3. When metered, from the switch side of the BLACK wire, and the UNLOCK button is pressed, it reads 12v.  SO, apparently I must have the wrong g****** wire since it seems to be working fine.  HOWEVER, as I stated in my last post, whenever I pulse the lock wire to +12v, it just sparks like it is shorting out.  I think there is a short somewhere in the vehicles wiring harness behind the dash that I cant find/get to.

oh, and btw, there is something not quite the same about this yukon.  because like i said before, there is no relay pack above the gas pedal like all the other ones, and, big suprise, THERE ARE NO BLACK/ WHITE OR BLACK/ RED WIRES IN THE HARNESS UNDER THE SPEAKER.  I know, shocking.  Thank you for trying to undermine my intelligence donut holes.

I apologise if any of my statements offended anybody,  all im trying to do, is finding out what are the posibilities that could have done wrong in the installation. As you had mentioned in the first posting. The lock / unlock switches work ( before the installation ) . That alone proved that there was no shorts or anything like that in the vehicle. You also said that the lock / unlock relays both activate accordingly when you used the remote. That means the remote is working.

This truck is using the 5-wire reverse polarity system, to find out the correct lock / unlock wires could be tricky. You didn't mention exactly how you probed the wires with your dmm. I suspected you had the black lead of dmm on the chassis ground all the times, then use the red lead to probe the lock /unlock wires while you press the lock / unlock button. If you use this method, you think what you see is what you get then you could be dead wrong, because I had been fooled myself.

What I always do these days, I would cut the suspected lock & unlock wires, then connect the red lead to the lock wire, the black lead to the unlock wire on the switch side. The dmm should read nothing at this point, then press the lock button, meter should read +12v, press unlock button, polarity should reverse i.e. -12v. If they don't behave this way, then they are not the right wires. Once they correctly identified, then each of them go to pin 87a of its respective relay. Of course, the other cut side of the wire go to pin 30.

I really like to see you have a happy customer.