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GMLAN data bus system

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by egcz71, Nov 7, 2012.

  1. egcz71

    egcz71 New Member

    Been doing some research on the GMLAN data bus system, but can't seem to find a direct answer. I purchased an aftermarket stereo and $5 wiring harness to install in my 06 Silverado. While I was reading about the wiring I came across the device known as the GMLAN data bus system. What exactly does this GMLAN do, where is it located and what functions will I lose by removing my factory radio? My truck doesn't have OnStar or the Bose audio system.
  2. wmkess

    wmkess Member

    I'm not 100% on what all it does do but I'm pretty sure it controls your door chimes. That system may also control your steering wheel controls if you have them.

    I literally just got my aftermarket stereo in the mail yesterday from Crutchfield, and mine came with a Metra GMOS-04 interface which keeps the door chimes as well as keeps the factory amp in my Bose system working.

    As to where it goes, mine plugs into the truck's harness and then the other side of the interface is wired into the plug that came with and connects to the stereo. So I would assume that the GMLAN is probably the truck's onboard computer system and then the factory radio contains the interface which outputs the door chimes and onstar sound.

    I don't really know much about this though, so don't take this to the bank. All I can say for sure is that you need some aftermarket interface if you want to keep the chimes.
  3. aloxdaddy99

    aloxdaddy99 Rockstar 3 Years 1000 Posts

    Most if not all the extras (Onstar, Factory Bluetooth, warning chimes, and I am sure I am missing something) all run through the radio. The harness keeps those things working. So in your case the only thing you need is for the chimes. PAC audio has one for like $50.
  4. egcz71

    egcz71 New Member

    So in reality I should be able to use the $5 harness to operate my after-market stereo and the only function I will lose is door, key and light chimes? I will admit that sometimes those chimes can get annoying, but I understand their purpose.
  5. wmkess

    wmkess Member

    I'd say so. Silverado radio's are so easy to remove and re-install I'd just try it with your harness and see if you notice anything else wrong other than the chimes. If there is a problem or you want the chimes back, it should only take a few minutes to hook up an aftermarket interface. And I think the price range on a basic interface is around $40 -50. I know there are lots on Amazon. I think Walmart even carries one in their audio electronics brand.
  6. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    Just a quick overview, the GMLAN is a Local Area Network that connects all of the control modules within the vehicle. The radio is only one of those modules, others include (as someone suggested) the Onstar module, the HVAC, the ABS, the Traction control, the Powertrain Control Module, the Transfer Case Control Module, the Door control modules, etc, etc, etc.

    The technician uses the ODB2 port and a TECH 2 analyzer to diagnose the systems.
  7. egcz71

    egcz71 New Member

    What I'm thinking about doing now is just using the $5 harness I have and then running a 12v ignition wire for the aftermarket CD player. I like not having the door chimes hooked up, but I would like to retain the feature that leaves the radio turned on after the key has been turned off. What circuit can I run the cd players 12v ignition wire to to keep that function?
  8. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    Only thing I know about the databus is that when I installed a remote starter I had to buy a special cable to connect to it,
  9. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    It's a Local Area Network; actually, may be considered 2 LANs, a high speed network and a low speed network. The low speed is used for the human to vehicle interface (push a door lock button, the door modules lock the doors). The high speed is for the communications between various vehicle control modules and their sub-modules (powertrain, body control, audio, brakes, etc). Most of the modules have 2 states, "awake" and "asleep". An idle state will induce some modules into the "asleep" mode, while others are commanded into that mode. The modules have battery power when the ignition is off, turning on the ignition commands the modules into the "awake" state. Things like the Retain Power feature, are software controlled; these modules stay "awake" for a defined time after the ignition is switched off. At the end of the defined period, the BCM (I think it's the BCM) commands these modules to sleep.
  10. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    Wow, Thanks [MENTION=54249]RayVoy[/MENTION] ! Excellent explanation.

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