Automatic Door locks quit working

[cowboywildbill]

Three of my automatic door locks quit working yesterday. The drivers side door still locks when you put the truck in drive and unlocks when you put it in park. The keyfob still locks and unlocks the drivers side door and will set the alarm. But the other three door locks don't work even if you use the inside lock switch. If I use the lock/unlock switch on the passenger side door armrest, it only locks and unlocks the drivers door. I checked the relays, I switched some of them around, there are other systems on the truck that use the same relay's. I checked all of the fuses. The only thing I'm not sure of is the relay that is on the passenger side of the dash, same little triangle shaped cover that is on the left with the fuses, only the right one has a relay, not sure if it is related to the locks. I don't have a schematic so I really don't know what else to try. I have an extended warranty, but if it is a cheap & easy fix, I just asume fix it myself rather than spend a whole day at a dealer. Any idea's would be appreciated. I guess I need to break down and buy a shop manual. Thanks.

[Modified]

You said you checked ALL of the fuses?
From what I see, the Drivers Door Lock and Unlock is powered from DR LOCK Fuse 20A, located in Fuse Block-Left I/P.
The other three doors are powered from LOCK Fuse 15A and UNLOCK Fuse 15A, also located in Fuse Block-Left I/P.
Reference Helms 2002, pages 8-1059 & 8-1060.

[cowboywildbill]

Thanks, I'll check them again.

[Mudflap]

I have noticed something wierd. I have a Motorola cell phone, when I plug it in to the vehicle charger my key fob remote door locks don't work. When I unplug the phone they work fine. My buddy has a K1500 gasser and his locks don't work from the remote either when his phone is plugged in. We both have AT&T. Strange

[cowboywildbill]

I checked all of the fuses again, they are all fine. I took my cell phone out and it made no difference. My key fob works my drivers door, the drivers door lock works just like it is supposed to, locks when you put it in gear ect. I just don't have any function in the other three doors. I guess I will have to go the the dealer.

[DmaxMaverick]

The possibilities are limited. There are two door lock circuits in the truck (as with most GM vehicles). Driver's door, and the remaining doors. The driver's door works independently, and the remaining doors work in concert, or are supposed to.

If the pass. door does not work in any case with the power door lock switches, the problem has to be a break in the communication between the relay and the door locks, or it is not getting a signal from the BCM.

Do the marker lights flash when you press the fob button the second time? If they do, the problem is after the BCM. If they don't, then the BCM is not getting the signal, or has been disabled through the programmable features.

I would suggest trying to reprogram the door lock events as described in owner's manual. Cycle through all the options. It may "wake up" the BCM and start sending lock/unlock signals to the relays. If that doesn't work, you'll have to start chasing wires. A good diagram is helpful. It is not likely a connector at the pass. door, or rear doors, as the pass. switch will unlock the driver's door, and the rear doors are effected as well.

Good luck.

[cowboywildbill]

Thanks, I'll give that a try!

[cowboywildbill]

I'm stumped. The drivers door works just like it should, the others don't respond to anything. The lights flash when you hit the unlock button on the fob.Nothing happens with the locks when you hit it twice, but the lights flash again. If you hit the fob twice for the lock mode, the horn will beep and the alarm will set, but the other three doors stay unlocked and if you open one of the other doors that aren't locked, the alarm will sound. :confused:

[Tommy turbo]

I believe ther is a seperate relay as well that works these three dooes . I am at home or I would ck the wiring diagram in my comp (it is at work) I could look tomorrow or you might look at the cover and see if it tells you. It does seem that it will be after the bcm since it does flash the lights ay the second button push. If The relays are the same it might be as easy as swapping the two door relays and see if symptoms swap as well. But if I remember right there are seperate lock unlock relays.

[cowboywildbill]

Thanks for your reply, I tried swapping the relays, but no luck. Any other idea's would be most welcome. I guess if I had a bad relay, I wouldn't know it. I guess there is a way to test them?