2024 Wiring light bar into high beams

[flymhi]

1 hour ago, rjgvt said:

@flymhi

 

Nice place for the upfitter switches. I put a 12v socket in that location and brought the wires through the dash at the  harness near the steering wheel.

 

Was the rest of the upfitter install the same as the other model trucks for the dash mounted fuse block?

 

 

The dash location for the fuse block on my 24 was not pre-drilled.  I simply drilled holes in the plastic backing and zip tied the fuse block in place.  It's roughly in the same area.  The plastic knee bolster panel still fits nicely and hides 98% of the block.  Here are more detailed shots.

Edited September 18, 2024 by flymhi

[newdude]

2 hours ago, CRApex said:

Thanks for the info! 

 

My current setup is safe and works but...I'm going to have to test this.  I just need it to trigger the relay, I wonder how they do it with a plow setup?  

 

 

There's a fuse kit in the plow prep equipment (can be purchased separately too and the plow mfgs sell a kit as well) to activate a 200 amp circuit for a plow, and then as far as lighting goes, looking at a Western for example it appears to be a standard plow headlight adapter like they've always made.  Plugs into the headlamp connectors directly inline and then the isolation module switches the lights when the plow is attached.  

[CRApex]

On 9/17/2024 at 10:51 PM, flymhi said:

I think I have found a spot to use as a trigger for the high beams (K9 BCM X2 pin 32 <wh>).  Just finished putting a light bar on my 24 Ulti-D.

You mentioned you thought you found a spot to use as a trigger for the high beams, did it work?  Thanks

[Conno.lund]

 I used the white wire in pin position 36 on the passenger headlight for my high beam trigger for my relay 

[CRApex]

On 11/19/2024 at 2:19 PM, Conno.lund said:

 I used the white wire in pin position 36 on the passenger headlight for my high beam trigger for my relay 

Is this on a 2024 with the LED headlamps?  

[BlackOutRST]

I'm going to add this in the hope it helps. I've looked everywhere for a way to work this out. I have a 2019 RST and adding the light bar to the high beams was a dream compared to this. We just put my wife in a 2022 Yukon and like you all, I hit a wall. I have not tried this yet but, wanted to add it here for you take look at before I forgot to add it. It's the closest thing I can find that gave me some direction:

I'm not saying this is right, so explore at your owe risk but, I'm going to check it out and report back (unless I set my wife's car on fire and you never hear from me again). 

 

I'd love for us to all find a solution for the group. 

Considerations

• Electrical Load: Ensure the additional devices do not exceed the module’s designed load.
• Compatibility: Verify that the ELM firmware won't block non-standard devices.
• Warranty Impact: Tapping into the ELM may void your vehicle's warranty.

 

Adding Relays for High-Load Accessories:

• If you're adding high-powered lights (e.g., off-road LED bars), use the ELM output to trigger a relay, with the actual power drawn from the battery or an auxiliary power source.

Using Auxiliary Control Modules:

• Some aftermarket systems integrate with OEM lighting modules via a CAN bus interface, allowing advanced functionality without splicing wires (e.g., app-controlled lighting, custom sequences).

Steps to Identify and Use the Output:

1. Locate the ELM and Wiring Diagram:

   • The ELM is typically found in the fuse block or near the vehicle's lighting control unit.
   • Obtain the factory wiring diagram for the ELM (usually available in the service manual or online).

2. Identify the High-Beam Trigger Output:

   • Look for the pin or wire labeled for high-beam output. This wire provides a signal (likely 12V) when the high beams are activated.

3. Connect to the Relay:

   • Use the high-beam output to trigger a relay. The relay protects the ELM from excessive current draw.
   • Wire the lightbar's positive lead to the relay's output terminal, with the power coming directly from the battery (fused).

---

Example Pin Description:

In a typical wiring scenario:

• High-Beam Signal Output Pin: Sends 12V when high beams are activated (consult the service manual for exact pin and wire color).
• Ground: Connect the relay's ground pin to a suitable chassis ground.
• Relay Trigger: Connect the high-beam signal output to the relay's trigger input.

---

Detailed Relay Wiring:

1. Relay Terminals:

   • 85 (Trigger Input): Connect to the ELM's high-beam output wire.
   • 86 (Ground): Connect to a chassis ground.
   • 30 (Power Source): Connect to a fused power source (e.g., the battery).
   • 87 (Output to Lightbar): Connect to the positive lead of the lightbar.

2. Lightbar Ground: Connect the lightbar's ground wire to the vehicle's chassis ground.

---

Why Use the High-Beam Output?

This ensures the lightbar operates only when the high beams are on, maintaining compliance with road regulations in many regions.

---

Caution:

• Verify the maximum load the ELM can handle to avoid overloading.
• Use a relay-rated fuse between the power source and the relay to protect the circuit.
• If unsure, consult a professional installer to avoid damaging your vehicle's electrical system.

[CRApex]

So I found a spot to use as a trigger for the lightbar relay.  Its the white wire coming out of the lighting module under the steering wheel.   Its the smaller module that's in front of the larger one.  I plugged a wire into the connector and ran it to the engine compartment and connected to the relay as my trigger, the light bar now works with the high beam switch.  Its been about 3 weeks and so far, no issues.

[SVTPaul]

On 3/11/2025 at 2:49 PM, CRApex said:

So I found a spot to use as a trigger for the lightbar relay.  Its the white wire coming out of the lighting module under the steering wheel.   Its the smaller module that's in front of the larger one.  I plugged a wire into the connector and ran it to the engine compartment and connected to the relay as my trigger, the light bar now works with the high beam switch.  Its been about 3 weeks and so far, no issues.

Hey, first off thanks for posting this! I'm going to be wiring in a light bar on my father in-law's 2025 Sierra 1500 Denali...figured it was going to be as simple as triggering a relay off a fused circuit for the high beams in the engine compartment fuse box but damn these vehicles are getting far more complex than they need to be!! I am guessing the white wire from the LCM gave you 12V hot wire? From what I read this is a pulse width modulated voltage that could possibly cause issues with the relay (as it is not the ideal type of power for a relay) or the LCM (concerning).

Did you happen to find which wire goes to ground from the BCM when the high beam circuit is powered? I'm hoping to find that and run 12V ignition source to the relay trigger and ground it to the BCM wire that goes to ground when high beam is activated. I'm starting to look around gmupfitter.com which I'm also new to and was hoping to avoid spending more hours researching this than doing the actual installation!

Edited March 26, 2025 by SVTPaul
typo

[CRApex]

On 3/26/2025 at 8:45 AM, SVTPaul said:

Hey, first off thanks for posting this! I'm going to be wiring in a light bar on my father in-law's 2025 Sierra 1500 Denali...figured it was going to be as simple as triggering a relay off a fused circuit for the high beams in the engine compartment fuse box but damn these vehicles are getting far more complex than they need to be!! I am guessing the white wire from the LCM gave you 12V hot wire? From what I read this is a pulse width modulated voltage that could possibly cause issues with the relay (as it is not the ideal type of power for a relay) or the LCM (concerning).

Did you happen to find which wire goes to ground from the BCM when the high beam circuit is powered? I'm hoping to find that and run 12V ignition source to the relay trigger and ground it to the BCM wire that goes to ground when high beam is activated. I'm starting to look around gmupfitter.com which I'm also new to and was hoping to avoid spending more hours researching this than doing the actual installation!

Not sure if its PWM but I can say it triggers the relay just fine.  I'm taking a chance on it causing an issue with the LCM but so far it has worked flawlessly and not caused any issues.  I did not find which wire goes to ground from the high beams, probably the safest route if you can track it down.

[SVTPaul]

1 hour ago, CRApex said:

Not sure if its PWM but I can say it triggers the relay just fine.  I'm taking a chance on it causing an issue with the LCM but so far it has worked flawlessly and not caused any issues.  I did not find which wire goes to ground from the high beams, probably the safest route if you can track it down.

Thanks for the feedback! It says in the system description that the power supplied to the headlamps from the LCM is PWM. In the below diagram from GMupfitter, it looks like there's a white wire (524) for high beam activation going to the BCM from the turn signal lever at X2 32. I'm new to all this and not sure if that's a pin location on the BCM etc...guess I better read up on what all the symbols and numbers mean. But I'm thinking if I tap into that wire to ground the relay trigger signal it might do the trick? It does also show a white wire (711 & 311) from the LCM to the left & right headlamps on the following page - that must be the wire you tapped.

Edited March 27, 2025 by SVTPaul

[CRApex]

18 hours ago, SVTPaul said:

 It does also show a white wire (711 & 311) from the LCM to the left & right headlamps on the following page - that must be the wire you tapped.

Correct, that is the wire I tapped.

[SVTPaul]

On 3/28/2025 at 1:06 PM, CRApex said:

Correct, that is the wire I tapped.

Thanks for confirming this. I'm going to use a solid state relay (no mechanical switching so hopefully shouldn't be affected by the PWM signal) and tap into this circuit also. I'm concerned that if I try to tap into the switched ground, I may only get activation when high beams are turned on from the turn signal switch (flash to pass or manual high beam) and miss picking up BCM ground from auto high beam intellibeam. I don't know enough about the system and since you have confirmed a proven method, I'll copy you. Thanks again!

[CRApex]

20 hours ago, SVTPaul said:

Thanks for confirming this. I'm going to use a solid state relay (no mechanical switching so hopefully shouldn't be affected by the PWM signal) and tap into this circuit also. I'm concerned that if I try to tap into the switched ground, I may only get activation when high beams are turned on from the turn signal switch (flash to pass or manual high beam) and miss picking up BCM ground from auto high beam intellibeam. I don't know enough about the system and since you have confirmed a proven method, I'll copy you. Thanks again!

That makes sense.  My setup has worked well with no issues.

[CRApex]

20 hours ago, SVTPaul said:

Thanks for confirming this. I'm going to use a solid state relay (no mechanical switching so hopefully shouldn't be affected by the PWM signal) and tap into this circuit also. I'm concerned that if I try to tap into the switched ground, I may only get activation when high beams are turned on from the turn signal switch (flash to pass or manual high beam) and miss picking up BCM ground from auto high beam intellibeam. I don't know enough about the system and since you have confirmed a proven method, I'll copy you. Thanks again!

Also, I inserted the wire into the rear of the plug, to avoid any damage to the existing wire.

[SVTPaul]

On 4/1/2025 at 1:52 PM, CRApex said:

Also, I inserted the wire into the rear of the plug, to avoid any damage to the existing wire.

Interesting you were able to do that - do you have a picture of how you did that by chance? I had planned on using a quality posi-tap (not the kind you crush together with pliers) but your solution is better again. Thanks