Dimmer 1 Circuit (b2610)

jsaddiction · May 1, 2009

I recently threw a B2610 DTC and after a day or so the SES light will extinguish. After a few more days it will come back. Are there any diagrams or common problem areas that I should check? I have a 2004 Silverado 2500hd LB7. A diagram of the "dimmer 1 circuit" would be great.

Thanks alot

Justin

bill190 · May 1, 2009

This seems to be a light dimming circuit on previous and older model vehicles (Inside vehicle). I don't know about your specific year vehicle. And this circuit goes to EVERYTHING! (With lights which dim as adjusted by the light dimmer.)

Have you made any electrical modifications to the vehicle? Installed a stereo or done any other wiring? Replaced anything which previously had a light on it which would dim when you adjusted the lights inside?

jsaddiction · May 1, 2009

no I don't have any mods... atleast to the dimming circuits. I have noticed a time or two that the lights on the switch would go out and come back on but it doesn't match with when it throws a code.

bill190 · May 1, 2009

Well if there was ANY wiring work done to the vehicle, I would check that as this is a common source of electrical problems.

This is the FIRST thing I look for!

With "do-it-yourself wiring work", I frequently find bare wires hanging, wires not properly crimped, but rather just twisted together and taped - then the tape has come off (can short to ground by touching nearby piece of metal), and protective black electrical tape removed to tap into a wire and the tape not replaced. The wires can rub up against sharp metal parts and intermittently short.

As to the "just twisted together" wires (rather than crimped), these will become a loose intermittent connection over time. They work themselves loose. And then dust will get in-between the connection.

Also they will tap into circuits and overload them. (Use more amperage than the circuit is designed for.)

After checking that, you say the switch is blinking on/off?

I would check for loose connections. This circuit goes to basically everything, so at this point, a general look at all wiring under the dash would be the best bet. A factory electrical diagram is just going to show you that this circuit goes to everything! So I wouldn't bother buying one for now.

If you can't find the problem, then maybe buy a factory electrical diagram (get these from dealer) and disconnect portions of the circuit and see if that causes the blinking to go away. (Something shorting.)

Or disconnect all but one known good light and power the other lights from another circuit temporarily to see if it is a "supply side" problem.

brims · May 1, 2009

Well if there was ANY wiring work done to the vehicle, I would check that as this is a common source of electrical problems.

This is the FIRST thing I look for!

With "do-it-yourself wiring work", I frequently find bare wires hanging, wires not properly crimped, but rather just twisted together and taped - then the tape has come off (can short to ground by touching nearby piece of metal), and protective black electrical tape removed to tap into a wire and the tape not replaced. The wires can rub up against sharp metal parts and intermittently short.

As to the "just twisted together" wires (rather than crimped), these will become a loose intermittent connection over time. They work themselves loose. And then dust will get in-between the connection.

Also they will tap into circuits and overload them. (Use more amperage than the circuit is designed for.)

After checking that, you say the switch is blinking on/off?

I would check for loose connections. This circuit goes to basically everything, so at this point, a general look at all wiring under the dash would be the best bet. A factory electrical diagram is just going to show you that this circuit goes to everything! So I wouldn't bother buying one for now.

If you can't find the problem, then maybe buy a factory electrical diagram (get these from dealer) and disconnect portions of the circuit and see if that causes the blinking to go away. (Something shorting.)

Or disconnect all but one known good light and power the other lights from another circuit temporarily to see if it is a "supply side" problem.

I found the headlamp wires on my El Camino to be that way. I was so happy when I found the wires to be like that. Some people should stay the hell away from anything that doesn't involve glue, glitter, and construction paper.

jsaddiction · May 1, 2009

Does anyone have any idea how the BCM decides how the dimmer circuit is malfunctioning. I work as an electronics tech for the Coast Guard and I understand everything Bill190 said. I have gone through all of the wiring behind the switch and all of my illuminated modules and can't find anything wrong.

bill190 · May 1, 2009

Does anyone have any idea how the BCM decides how the dimmer circuit is malfunctioning. I work as an electronics tech...

I've had a difficult time finding technical stuff like this for automotive computers. This information if available by the bucketloads for ANYTHING else!

If you're an electronic tech, you probably have access to enough technical information to build your own gizmos from scratch (almost) for what you work on. But automotive manufacturers don't like to share this stuff!

I've noticed some circuit monitoring of things like air bags will use "end of line resistors" like with a security or fire alarm system. And I sometimes see switches and such in automotive electrical diagrams with resistors added in parallel with the contacts. This might be for circuit monitoring. Yet there is no technical explanation in the repair manual for this!

I suppose the BCM could also look at the signal and be sure it has what it should have. Then if nothing there due to a short holding it to ground, flash the diagnostic code. Or maybe a return loop and look for the signal to return, then if nothing there flash the diagnostic code. Also if something there when nothing should be, short to high. (I'm just guessing.)

The following link is for Automotive Electrical and Sensor Engineering discussion. These guys might know how the BCM might monitor the circuit. Might want to ask a general question there about how the BCM works to monitor this circuit as opposed to "How do I fix my car". (More for technical discussion.)

http://www.eng-tips.com/threadminder.cfm?pid=67