Remote Unlock Intermittent

[Tenaya43]

I have a 2004 Silverado LT Crew Cab.

 

Previously I had problems with the rear doors not locking. That was remedied by replacing the relays, but recently I've had a new maybe related issue. 75% or more of the time, the remotes do not lock or unlock the doors. The lock/unlock switch on the drivers door works reliably all the time. I thought it was the remote(s) and/or syncing, but I was able to re-sync both fobs. Plus, about 25% of the time, the remotes work properly. Complicating this even more, when the remotes aren't working, after pressing the driver's lock/unlock switch one way or the other or both the remotes sometimes start to work. For a while. I thought the issue might be temperature related, but the issues occurs well below freezing, above 100 degrees and every temperature in between.

 

SO, I'm now thinking that whatever module actually controls the removes (and/or central locking) may be at fault. Can anyone tell me which module is responsible for these functions and where its located in the truck?

 

Thanks,

 

Tenaya

Edited July 26, 2019 by Tenaya43
Forgot to mention that the drivers door lock/unlock works all the time.

[davester]

For my '04 Sierra (extended cab, so just front locks), the remote only works if the doors are fully closed.  Maybe a sensor/wire isn't quite right, and sometimes the bcm thinks one or more of the doors are open?

[Tenaya43]

davester,

 

Hmm. The next time it's acting up (read: the next time I go somewhere in the truck), I'll have to try opening and closing the doors a few times and see if that makes any difference.

 

I'd still like to know which module does this stuff and where it's located so I can unplug/plug the connectors a few times and clean the contacts. This approach to intermittent problems has served me well in the past.

 

Thanks for the tip.

 

Tenaya

[intheburbs]

I hate to be Captain Obvious, but do you have fresh batteries in the fobs?

[Tenaya43]

14 hours ago, intheburbs said:

I hate to be Captain Obvious, but do you have fresh batteries in the fobs? 

Yes, I made sure the fob batteries are fresh, new, actually. Additionally, the fobs work properly . . . sometimes . . .  and have good range when they do work. I'm pretty sure the problem lies elsewhere.

 

Yesterday, I tried two things:

1. At a time that the remotes were NOT working, I open and slammed closed all four doors several times, one by one, trying the fob each time. This had NO effect on the problem.
2. I removed the Drivers Door Module (DDM) fuse for about half an hour. This had NO effect on the problem and did NOT make it worse (i.e. it remembered the fobs).

While the DDM fuse was pulled, the central locking system did not work at all, including the door lock/unlock rocker switch.

 

What I'd like to try next is to unplug, clean the contacts and re-plug which ever module is responsible for the function of the fobs.

 

I'm now certain that the DDM controls central locking, but does the DDM control the fobs (i.e. receiver, etc.)?

• If so, where is the DDM located? Is it in the driver's door armrest?
• If not, which module does this and where is it located?

Thanks,

 

Tenaya

 

[rjgti]

resync the remotes by holding down lock/unlock on remote from outside truck for 7 sec or until you hear the locks cycle

Edited July 30, 2019 by rjgti

[Tenaya43]

 

11 hours ago, rjgti said:

resync the remotes by holding down lock/unlock on remote from outside truck for 7 sec or until you hear the locks cycle

rjgti,

 

Thank you for your suggestion.

 

Even though I've re-synced the remotes several times recently, I went out to the truck an hour ago and tried it again. The truck was in the mood to cooperate (that is, both remotes were working at the time) and I was able to successfully re-sync both remotes (the locks cycled). After re-syncing, both remotes worked properly, close up and from about 25' away. So, I locked the truck and went on about my day.

 

10 minutes ago I tried the remotes again and neither one would unlock or lock the truck. I cycled the driver door lock/unlock switch (sometimes doing that works, sometimes it doesn't help at all), but both remotes remained non functional. I also tried again to re-sync each remote, but neither responded in any way.

 

I still suspect whichever module it is that controls the remotes. If that's correct, my next step would be to unplug all of that module's connectors, clean/burnish all the contacts and reconnect it. BUT, I need to identify and locate the right module first.

 

Does anyone know which module does this and where in the truck it's located?

 

Thanks,

 

Tenaya

[davester]

I would suggest getting a subscription to the full-service manual for your truck.  It's not that expensive, and it includes the complete wiring diagram for your truck, diagnostic procedures for figuring out this problem (may require a tech ii or similar), as well as the location of where the various computers are.

[Tenaya43]

I finally got the chance to take the passenger door apart. The window/lock switches are actually a module with PDM embossed on it. I assume PDM stands for Passenger Door Module. Interestingly, it also has the Motorola logo on it.

 

Written on it in marker are SILVERADO and 2003. Since wrecking yards commonly do this, I assume it was replaced sometime before I bought the truck (over a decade ago).

 

The module has a sticker with 15191372 (part number?)and PDM w/ US RFA and FCC ID: LHJ012 and CANADA and 109G 1202D printed on it.

 

The web tells me that RFA means Radio Frequency Allocation, among other possibilities (it probably doesn't mean Royal Field Artillery). RFA, the Motorola logo, the presence of an FCC ID and some Internet reading about GM key-less entry all lead me to believe that this module MAY contain the actual FOB receiver.

 

As per my original plan, I unplugged the module, cleaned all the contacts (they all look good) and plugged it back in. That didn't seem to help. I don't know if the problem is still intermittent, but the fobs don't lock/unlock the doors at the moment. The fobs may work later, according to its previous behavior. The manual lock/unlock switches on both doors work properly, as they always have.

 

Before I replace the module, can anyone confirm that the PDM actually does have the fob receiver in it?

 

Thanks,

 

Tenaya

[04chevy209]

Try cleaning the bcm or get a second bcm to test yours from a buddies truck or junk yard. It’s a small square black box that should have 4 plugs. It’s right above your feet under the steering wheel. You’ll need to remove the plastic cover. It’s a tight spot but that body control module is what you’re looking for I believe. 

Edited November 16, 2021 by 04chevy209
Misspelled

[Evan Johnston]

Did you ever solve this? My brother's 2013 GMC Sierra is doing the exact same thing

[Ak_grown]

Check the battery brackets on the remote fob circuit board. Solder connections could be broken from circuit board, reheat and dap fresh solder. Repaired many of these and remote start fobs with same issues.