Metal.Dave

I had the same exact symptoms, found the broken wire, it's behind the big wide connector thats mounted on the plastic bracket, above spare tire.

I did see a flash module from some brand advertising on insta, from what I remember the price was around $500 so I gave it a fat pass. Its one of those things I might use a few times a year so not worth the price for me, but seems easy enough to tap into a few wires and make a DIY flasher while im at it doing the LED bar and aux lighting.

Wanting to add a strobe mod to the roof clearance lights. Where is the easiest location to tap into the + wire? 1- Pillar (driver or passenger?) would be looking for a violet/gray wire correct? 2- Or near the control module, I am guessing it goes to the K9 BCM in the driver footwell area same as headlight BCM? If so what color wire on what color connector? I know I will have to add in some type of double throw switch to disconnect the OEM wire and close the circuit on the strobe. Also want to tap the fender marker lights into the same strobe module, those are pretty easy to find and access at each fender, but instead of running multiple wires to each one- wondering where can I find the central + wire to tap into? From my understanding it looks like each fender marker is independently fused? Tagging @newdude here because he seems to be a pro in this stuff. Thanks in advance!

Im guessing that the timer function for the reverse / cargo lights on the mirrors is activated and controlled by the BCM, so tapping into the fuse or signal wire would be useless anyways as the timer function wont be active unless the reverse / cargo lights are active. Unless someone has studied the wiring diagram and can confirm otherwise- Project has been scrapped. For now I will have to go with a always hot fuse.

Hey all! Got a 2021 L5p Looking for an unused auxiliary fuse that is on a timer, meaning it will cut power after 10-15 minutes if truck is not running, same way that mirror & cargo lights shut off after xx minutes. I am guessing the upfitter kit uses a timed fuse? But cant find any info on that to confirm. Thanks!

Ok I checked it today and confirmed- it is in fact a momentary signal / circuit. It works even with all light switches off, vehicle off.

Imagine how convenient it would be to toggle between white or yellow high beams!! That's a hidden extra feature not a glitch! But yeah I will put in a secondary switch.

If its a momentary signal, A latching relay should do the trick (i think thats what they call it)

I am trying to install a yellow/amber LED bar high beam so I have yellow only high beams controlled by the high beam stalk. (for heavy snow and foggy nights). Plan is to see if that is possible when the headlamp switch S30 is set to running lights only In running lights only position, the high beam on trigger does not turn on high beams, but I am hoping that if I tap into the signal wire from the stalk switch (before BCM) I will still get an active circuit. Im not all that good with wiring diagrams so cant tell if circuit 1851 / headlamp switch may prevent this from being possible. If possible, I will use it to power the lowest power draw relay I can find, that relay will energize power to LED bar. Because the high beam-on stalk movement is like a momentary switch (stalk returns to neutral position, and does not stay engaged like the older cars did) I may run into more complications as Circuit 524 white wire may not be a constant closed circuit when high beam on is triggered, and may be a momentary signal which the BCM then controls to constant signal until circuit 307 yellow/brown stripe high beam flash signal is triggered which is also the high beam off function.

Appreciate the response @newdude ! So I was testing it wrong after all.... Ok to clarify- I should be testing for continuity to ground on Circuit 524 white wire, and when high beam on is triggered I should get a closed ground circuit?

Hello fellow GM owner! I got a 2021 Sierra and I am trying to find the high beam on signal wire coming from the multifunction switch (turn signal / high low beam stalk switch). There has to be 2 signals wires, 1 functions to momentarily flash high beam, 2nd one functions to constant on high beam. I am assuming it functions on the principle of + comes into the stalk switch, when triggered it sends the + signal to the high beam relay. (this assumption may be wrong) Truck is off- all acc are off, most of the wires should be dead with no +signal (from the way I understand it) I took off the steering column plastics to expose the harness going to the multifunction stalk switch and needle probed each wire with a multimeter looking for a switched + signal when the high beam is triggered. There is about 12 wires there, nearly all had a constant + 12V, a few had no signal. I followed the steering column harness down to the footwell area where it goes into a BCM, green connector, probed every wire on that connection, nearly all had a constant + 12V, a few had no signal, and one wire triggered +12V on the high beam flash switch, but then it remained constant on 12V+ even after the high beam was off, no voltage bleed out/ drop to indicate it was just a capacitor charge, and there shouldnt be capacitor on the high beam signal wire anyways. I am completely stumped! Why does almost every wire have a 12V+ charge when everything is turned off? Why cant I find the the 2 high beam signal wires? Is my understanding wrong of how the electrical system works on these trucks? And yes I specifically need to find the signal wire coming from the stalk switch, and no I cannot use the high beam + load wire after the relay as the signal wire instead.

Thanks!!! I will reach out to ultraguage and see what they say.

Wanting to put in a UltraGuage, and one important PID I need to see is trans gear selection. From what I know, the Ultragauge does not have that capability without some kind of coding/ programing. Has anyone successfully done it, and if yes can you share the process?

I am convinced that the trailer is not the issue because I can hook it up to another truck at the yard and it works just great! It seems as if though truck has some intelligent system for detecting trailer brake types and adjusting voltage output for those kind of brakes but theres some inherent issue with the technology....

So I'm having a weird issue with my 2021 sierra 3500Hd trailer brake controller. The issue: - Hook up trailer #A, when empty brakes needs to be set below 3 to keep tires from locking up. - Hooks up trailer #B, also empty, turn up controller to 10 and I barely feel any braking force from the trailer when manually pushing the slider all the way. I can hear the electric brakes working on the trailer, it's just not giving enough braking force.... so it's not the same issue that others are having where it's not working at all... -No error messages on dash. - both trailers are dual axle and have about the same empty weight. >● If I hook up either trailer to another truck at the yard (Ford or ram are the only other options) the controller needs to be set at 3 or below also to keep tires from locking up. This test rules out any trailer issues! I have searched Google and the forums and could not find any solution! Some people have tried replacing the sliding push control in dash, No luck. Browsed through hundreds and hundreds of forum posts, no solution found......

So I'm having a weird issue with my 2021 sierra 3500Hd trailer brake controller. The issue: - Hook up trailer #A, when empty brakes needs to be set below 3 to keep tires from locking up. - Hooks up trailer #B, also empty, turn up controller to 10 and I barely feel any braking force from the trailer when manually pushing the slider all the way. I can hear the electric brakes working on the trailer, it's just not giving enough braking force.... so it's not the same issue that others are having where it's not working at all... -No error messages on dash. - both trailers are dual axle and have about the same empty weight. >● If I hook up either trailer to another truck at the yard (Ford or ram are the only other options) the controller needs to be set at 3 or below also to keep tires from locking up. This test rules out any trailer issues! I have searched Google and the forums and could not find any solution! Some people have tried replacing the sliding push control in dash, No luck. Browsed through hundreds and hundreds of forum posts, no answer found. Does the truck have some "intelligent" trailer weight sensing feedback system that could be causing this issue? Is there a specific procedure for hooking up trailer and setting controller, that if done wrong will give low braking force? Thanks in advance!