BCM Question

This question will require a little background first.  When I bought my truck I was disappointed to learn I could not get Homelink as an option.  Not being one to take "no" as an answer, I picked up a used overhead console from ebay that had the 3-button Homelink transmitter in it.  It was from a Burb.  I took out the rear a/c controls, swapped in the storage compartment from my truck console, and viola- I had what I wanted.  The connector on my new (homelink) console plugged in perfectly with the existing  plug in my truck.

The connector had 3 wires.  I'm pretty certain they are +, - and bcm.  The bcm thinks the console with the map lights is there, hence the homelink button LEDs light up when the dome light comes on.  They do not light up at night.  What I want to accomplish is to have the buttons light up when the headlights come on, and be controlled by the dimmer switch.  I want the buttons to behave just like the window/lock controls on the door or the head unit controls.  My understanding is that the bcm controls the dimming feature.

Here's my question-  where do I find the bcm wire for the passenger door?  I know where that harness is on the side of the dash, I just need to know which wire in the harness is the bcm wire that controls the LED lights in the armrest.  Once found, I plan to splice into it and connect with the bcm wire going up to my console.

Thanks for any help.

Not sure if that will work or not. If the bcm is causing the lights to light up it may see it as a bad signal. I dont think they light up from the factory do they? (might be wrong on that one)

They do.? Our Burb has the same console.? At night there is a small white dot in the middle of the buttons which lights up and is controlled by the? dimmer switch.

The BCM provides an LED source and an Incandescent lamp source.

The front doors are connected to the BCM/data bus from the door modules.

Here's some drawings of the interior lighting:

The images expand; how, depends on your browser.

More:

Connector 1 of the BCM is the small one on the left. Look for the purple wire with the white tracer.

That's your LED dimming supply.

Now, I hadn't had that upper console off. Are we certain it's LED illuminated? Perhaps it does source to the other, as the print shows and it is incandescent?

They distribute certain portions of info to other prints often.
Here's more of the console... on the roof beacon diagram!

HTH!

Thanks Sperry.? I am assuming they're LED.? There are no obvious bulbs.? The best analogy I can come up with is that they appear identical to the lighting under the buttons for the windows, mirrors, driver recall and door locks on your door arm rest.? I would say the lighting is identical for the 3 buttons in the console.?

I am not the most literate when it comes to reading wiring schematics.? Do the Avs have these homelink buttons in their overhead consoles?? I did not see the transmitter referenced in the drawings, unless it was the "roof beacon."? The standard console that came with the truck had no LED lights or buttons that were backlit.?

Except for the theater spots/courtesy overheads, It's on the last diagram.

I don't believe it was on the standard equipment list. I did get it though. Either it was part of the Z71 pkg or the seat-console-interior pkg... I'd have to dig through the RPO list I had on my truck, wherever that is?

Thanks again Sperry.  I apologize for being dense, but which diagram shows the bcm going to the driver door harness?  Is the purple/white wire you reference the bcm feed in the door harness?  Sorry for not getting it, but I think the feed I need would be the bcm that controls the backlit buttons for the door.

That is only on the class II bus. One wire, not a harness. All those things you fiddle with on the door... One wire* to the BCM (and other places like seat modules if you have butt warmers, pass ft. door...)

In the attached pic, you will see multiple connections for the seat. Those are the seat warmer buttons and indicator - still in the door.

*That's not counting the power and ground (at least) of course.

02 & earlier had more, and your rear doors are controlled by the BCM directly, so they have multiple conductors..

Top: Driver Door Module - Lower: Front Passenger Door Module. These are partial.

The images expand; how, depends on your browser.

Rather than prolong this, let me just ask it this way.? In the door harness located in the fuse panel on the driver's side end of the dash, is it the purple/white wire that contains the bcm info that controls dimming of all the door switches?? If not, what color is it?? Which pin is it in the door harness??

Sperry, I appreciate all your patience but I'm afraid I don't have enough "engineer" in me make sense of the diagrams and your explanation.

Edit-  I've checked the door harness in the panel on the end of the dash and there is no purple wire.  I saw orange, black, and assorted pastels. 

The single purple-white wire is from the left-most connector on the BCM. That's a 6-way connector, like the one on the far right of all the others in front. It is a power source that connects to the common bus for the LED's that dim. Not a controller in it's own. And not part of the door harness.

The wire can be tapped at that BCM connector point, instead of tracing it out through the dash wiring.

The LED source in the (front) doors are, if I remember correctly, sourced from the door modules, for each respective door, inside them. The door modules decode the dimming data from the common data connection and provide the dimming source for the LED's in the doors.

The dimming source for the LED's within the instrument panel parts, such as the overhead console or small indicators, is the purple/white wire at the BCM. That will "Track" to the same dimming as the door LED's.

Most of the confusion is that one expects a discrete wire for each switch or light on the door, all passing through the door harness. That just isn't so in this case. In 03 and later (to this extent), variables such as rolling down another window, adjusting the pass mirror from the driver side, seat heaters, etc., are not through discrete wires. They are encoded or decoded by the door modules and sent by the serial data link wiring to/from another module, on a common, single (future will be a pair) data wire.

And this isn't exclusive to the front door modules.

The rear doors have less to consider, so they are discrete and use the BCM to decode data and supply the necessary voltage or command to them. (Window up/down, locks, door open switch, etc.)

I don't expect you to know this overnight! It does take a bit of study in this field. When someone who may of dabbled with wiring in earlier vehicles comes onto this method, well! I would certainly expect a bit of difficulty by many trying to make any sense of it.

Here's some reading that may interest you.

I don't mind helping.. As long as we can get somewhere with it.
If you just simply want the LED's in the upper console you bought, forget the door LED connections for now. Let's look at the BCM source instead.

Sperry-  I'll follow your guidance on the best way to "get there from here."  I was just trying to figure out which bcm line was already doing what I want done in my console.  My truck's "brain" doesn't know the homelink console is there.  It thinks the old cubby hole console w/ 2 spot lights is there.  Ergo the bcm commands it gets just say "come on when the door is opened or the key is pulled out."  The doors are getting the command I want sent to my console, i.e., "led lights come on when the headlights are on."  I will trust your judgment completely on the best way to accomplish this.  Just tell me which wire in which harness in which panel to try.  Thanks.

The LED dimming wire is at the BCM. Tap it and run it up to the upper console. If you have LED's for something else that's already up there, THEN we'll look into tapping that.

I don't remember the LED's lighting other than when the button is pressed and/or programming. That just runs from the module itself.

The homelink is totally independant of the vehicle's data system. The ones at the buttons operate only when the homelink is transmitting or programming. The module runs off a constant power source. The lamp connections should be for the courtesy lamps, ground (May be a local fastener) and constant power. If there is no constant power there, THAT is what you seek. You can tap that from your fuse box, of course. Likely a 1A fuse is plenty, but a 3A is still safe.

So, advise me again of what wires are in your truck up there... And I'll take another look here in a few when I go out on an errand...

BTW, here's the training procedure.. HOMELINK TRAINING

OK, stupid me (early Alzheimer's?).. The buttons have those light's which dim, however it appears to be incandescent lamp(s), not LED's! So, back to reviewing your wiring.. (The blinking ones to indicate activity are likely LED's but that's from the homelink module.)

I/P dimming supply bus - Dims/Brights the button lights: Brown/White wire
Inadvertent power supply bus - Powers the logic: Grey/Black, for circuit 1732.
Courtesy Power supply Bus - For the courtesy mode, as switched: Gray/Black wire for circuit 690.
Ground: Black

Obviously the two wires for the two spot lamp modes are the same color and different circuit/function.
You will need to ID these by function to isolate them, obviously.

So, the next step is to inform me of what wires you have up there again.... Sorry!
Isolating things this way is a bit awkward, so I'll keep at it for you until we can sort it all out.

Here's a picture of what the console looks like.  I have removed the a/c controls and put in my cubby hole insert.  The lights I want to control are the little white dots in the center of each of the homelink buttons.  I guess schematics for a Suburban or Tahoe might say whether they're led or incandescent.  There is a flat 3-way connector up in the console, it powers both the homelink and the spot lights.  No wiring changes were made in the console.  I'll have to check the colors later, I believe they were orange, black and grey or white.  As an aside, here's a link to some wiring changes I made at the fuse block to keep constant power to the homelink unit:  http://dieselplace.com/forum/showthread.php?t=36893&highlight=homelink

I'm going to be out of town for a few days (thinning out the deer population) and will let you know the exact colors of the wires.  Thanks Sperry.

OK! yes, the `burb & Tahoe would have the rear control wiring we ignore here.

The diagrams above are general. The rear control diagrams would be separate and of course, SUV specific.

I really doubt the button center lights are LED's, as the diagram shows an incandescent lamp and the dimming source used is for those filament lamps.

There's only the one LED for button / send & program activity. It's not part of the dimming circuit.

-----

Have fun with the deer population control.. A friend of my bro's (his friend's nephew) poped a young buck 3x3 Pt. on the first morning. (Mule deer) Not a tick or any sign of a health problem.

So, get lucky!

Sperry,?

I've had a chance to take a peak at the wiring up in the console.? The 3-wire lead which comes to the

console is orange, black and gray.? I believe these to be power, ground and bcm? signal.? The lead is part

of the HDLNR 12 WAY harness on the fuse block located under the dash.? I think we are both on the

same page now about the buttons I'm referring to.? It's the little white dots in the center of the buttons

for homelink that I am trying to control.? Right now, the buttons are backlit only when you turn on the

dome light or when you pull the key out of the ignition.? I want to tie the gray wire into a bcm circuit that

activates the light behind the buttons whenever the headlights come on, similar to the lights behind

the various buttons on the driver door armrest.? I will trust your advice on the best way to accomplish

this.? ?If possible, let me know which wire in which harness in which fuse block I need to splice

into.Thanks again for your patience.

It sounds like you have the button indicator connected to one of the the spot's circuits. What do the spots do. Operate normal? (Courtesy or manual spot.)

When I "upgraded" the console, I simply plugged the existing connector into the connector that came

with the 'Burb console.? The console is still getting the same bcm signal it got when the factory console

was there (i.e., 2 spots, no homelink).? That bcm signal simply says "light up when dome light is on or

when the key is pulled."? The 2 spots still work when you push the buttons, they don't come on with the

dome light anymore (not a concern to me).? My theory is that the "courtesy" signal only makes it to the

homelink buttons, that's why they light up with the courtesy lights now.    All I did was install a different

console in the same spot.? The only wiring changes I did? were the ones referenced in the link above to

get constant power to the console.? Now I want to fix/change the bcm signal the console gets.? I want it

to get a signal like the bcm signal that goes to the doors- that's why I keep coming back to the door

circuit.? I may be missing something or over-simplifying, but it seems to me that the bcm wire in the door

harness would be a simple solution to my problem.? Can you tell me which wire in the door harness

carries the bcm signal that controls all those backlights on the buttons in the door?? I think that's what I

need.

It sounds like two wires are swapped. The courtesy light source is to the buttons, instead of the door light mode of the spots. And vice-versa.

As far as the door wiring for the lamp control, that's all from data. the wire is only to the DDM inside the door. then it's by data to the BCM. It's not a set of discrete wires. So one taps the BCM for the necessary source, not the door "harness".

If I was there with a voltmeter maybe..

Use the diagrams. download and print them. If it isn't your thing, perhaps a buddy can look them over for you. Text help Just may not work so well in this case.

If I only had access to look at the Silverado version of the upper console wiring..
From what it reads like,  they shifted wires over a notch and you connected it only to find operational changes.

sperry said:

As far as the door wiring for the lamp control, that's all from data. the wire is only to the DDM inside the door. then it's by data to the BCM. It's not a set of discrete wires. So one taps the BCM for the necessary source, not the door "harness".

Click to expand...

Let me try it this way-  Where is the bcm source that goes to the door?

The top diagram in my post #3, shows an i/p dimming supply bus from BCM connector 1 that will dim your button lights, Now that I see it's NOT illuminated by LED's.

If you prefer to tap onto a door connection instead of an under dash connection, you can run your wire through the door harness, inside the door and tap onto the circuit for the lamps in the door. Why you prefer to do that is your own reasoning. I was under the impression that you would want an easier way to do it. Sorry!

The door lighting info I find in the GM prints only cover the courtesy circuits and the background lighting for the seat heater buttons. So I have no door interior info to guide you with, for this illumination connection you seek. Perhaps a factory manual will have that. (Helm-Inc)

If you do prefer an easier way, you can unlatch and fold out the relay block (The electrical center at the firewall area, above the driver's left toe), to identify the massive number of brown-white wires from the relay block. (Mostly it's connector #1.) The connector is the largest one on that relay block. If the door module does not supply this illumination for the door lighting (which I cannot determine, due to the service data I have). Chances are that some of those brown-white wires are fed to the doors. One does feed the upper console in the Av/`burb diagram.

If you tap one of these wires, you won't need to remove the knee-bolster to access the BCM connector in this case.

These wires source the many distributed instrument lamps. (Incandescent ones.) If you connect the lamp that illuminates the three homelink buttons on the upper console to one of these brown/white wires, you will properly illuminate it, providing the rest of it's circuit is properly wired. (the ground, connector wiring, etc.) By the diagram, the homelink module sources the lamp and the brown/white wire sources the homelink module. That doesn't make sense, unless the lamp shown is just the activity indicator. So, without tearing mine down, the prints are all I can use.

Other dimming supply source locations are also available, such as the right dash connector block. ("Left I/P" as they call it)

A service manual for your truck is available from Helm-inc.

Good luck!

Thanks Sperry.  I definitely want the easiest approach.  Is it the INFO or BODY 12 way you refer to as connector 1?  Here's what the IP looks like:

The image appears a bit different but the location and all sounds right. First off however, is there a brown-white wire in the above console harness/connector? If not, THEN look for the brown-white wires mentioned earlier. They just junction down there. Functionally/electrically, the wiring is the same. So, do for the easiest/closest one. Maybe use an automotive test light and see how it'll track with the instrument lights on.