That just further confirms my thoughts on what is happening. I'm going to try and write something coherent in a minute but can you indulge me one more time - confirm that your horn is working or not.

 

horn works. Please tell me this is a inexpensive fix? I'm scared to see what you say now....

 

Put it this way, either this will be a cheap easy fix or a warranty claim. Can you take a picture of where you made your splice connections for the mic?

 

The truck is outside in the dark. I pulled off the passenger kick panel and there was a connection that matched the one in the diagram. I spliced in the two that were shown. They are colored blue and yellow with a green stripe I think. I can try to rig something up if its vital..... The harness looked like it was running to the back of truck under the kickplate.

 

That's okay I am actually more interested in the violet with grey stripe wire that is in the connector near the splices. Did you take the connector apart when you made the splices?

 

yes i did. it had some type of red safety pin in there as well that you had to remove? What type of problems do you have in mind?

 

I just took a picture of the connector in my truck. I'll post it up here in a bit so you can look at what I am looking at.

 

Wow, you are going above and beyond for me. I sure hope its the cheep easy fix?

 

Okay here is the picture and why I am so interested in it:



First off, the way the dimmer system works in this truck is that it is all electronically controlled - no mechanical rheostats, etc. There is one "dimmer brain" which is housed in something called the Steering Column Control Module or SCCM. That brain monitors the dimmer switch on the panel. You can see the brain working when you go into the engineering test mode and look at the dimmer values that can change between 13 and 18 as you did earlier. Those values get sent by the dimmer brain to help control the lighting levels.

The backlighting system is actually composed of 4 main modules or components. They are the Instrument Panel Cluster Module, the HVAC Module, the Audio Control Module and last but not least the Body Control Module.

The SCCM brain's only function (with respect to lighting only) is to monitor the headlight and dimmer switch positions/activity and then relay that information to the BCM. The BCM then does two things simultaneously. It sends a message on the CAN Bus to the HVAC, ACM and IPC modules telling them what position the dimmer is in. These three modules then independently adjust their backlighting accordingly. If the message gets garbled or don't respond appropriately they will default to either the last position before power off or to night light mode ultimately.

As for all the backlit switches, there are two types - networked and non-adjustable. Non-adjustable switches are as examples the door locks and power window switches. Everything else however is adjustable by the BCM. This is where the violet wire comes in.

The BCM controls LED lighting on the switches by sending a pulse modulated voltage (likely 5 volts). Essentially the shorter the pulse width, the brighter the LED. It determines the pulse width from the SCCM reading. When everything is harmonious, all four systems while operating independently of each other appear to us humans as a symphony of light - okay perhaps that is a slight exaggeration.

So, based on all this I suspect either that purple wire got damaged or disconnected somehow near the splices or it is a bad BCM.

Take a close look in the daylight at that connector and the purple wire for any signs of damage. If you have a voltmeter, you can test it to see if the BCM is outputting a voltage on it.

 

Ok, Im going to check that wire in the AM. Is it possible that I messed that wire up when splicing? I guess thats the easy fix. What happens if its the bad BCM?

Do you know anything about the mic not working either? Im thinking that the plug is not insterted correctly or something? Because both of those things are on the same harness and both dont work?

Is a BCM easy to replace? Cost?

 

Also what type of voltage should I be looking for? AND thank you so much. If you have paypal or something I can wire you some dough. You don't know how much I appreciate your help. Ill let you know what i come up with in the AM.


Is there anything else on that connector that would not be working? Looks like alot of wires there?

 

Nah, I like doing this stuff - keeps my brain from turning to mush.

First thing you should do is pull the connector apart and inspect the pins for any damage - particluarly pin 9 which houses the violet wire. Check to see if the pins got pushed back or anything. While you have the connector apart, check the wires for any damage, nicks, cuts, solder burns, etc. Anything that could disrupt the continuity. If that all checks out then snap the connector back together and proceed to the next step.

Next, if you have a continuity tester, check the purple wire before and after the connector to ensure the mechanical connection is good. If that checks out, time to check for the pulse, literally.

Actually, you won't be able to see the pulse specifically but we are more interested in if it is there. Take your voltmeter and stick a probe into the purple wire and ground the other. Normally with no pulse (i.e. 100% duty cycle), you should get a reading of anywhere from 3 to 14 volts if the BCM is sending the signal properly. However, since we don't know the duty cycle, a voltmeter may measure very little - I will poke mine tonight to see what kind of readings I get and post back.

 

You will also note a handy ground location in the picture above. You can just see it at the top and slightly right of center.

 

Okay good news, you can read the voltages. With the truck on and full illumination on the dimmer I get a reading of just north of 14 volts - basically alternator voltage meaning almost 100% duty cycle. At full dim I get a reading just shy of 3 volts so looks like around a 20% duty cycle when on the lowest illumination setting.

What this also means is that you can test these circuits with a regular 12 volt test bulb if you don't have a voltmeter.

I tested above and below the connector - here are some pics of my setup. Top pics are full illumination with readings above and below connector. Bottom pics are full dimmer.

 

Okay one last thing - I am out of town tomorrow and back Sunday evening. I may have 3g access but not sure so I may not be able to check back here until Sunday.

In any case, if after doing your testing you still can't find where the continuity is being cut the next step will be to run the voltage test right at the BCM source - it is pin 40 on connector C2280B but I will need to rig up something and shoot some pics when I get back.

Also, just double check that your dimmer still works on the radio, instrument cluster and HVAC controls. If they don't work its most likely a bad BCM - that would be a warranty claim for sure. One other possibility is the BCM has gone into a failsafe mode to protect itself - this may be resetable at the dealership - for sure there would be DTC's being thrown by the BCM which can only be read by the dealer scan tool. They will know straight away.

However from everything I have seen, I still think its a wiring continuity issue. Once we get this working we'll sort out the MIC issue - pretty sure that one will be a lot simpler.

Good luck/happy hunting/etc...