What does the BCM do if you remove 3rd brake light?

[Yellow Cake Kid]

Hi,
I have been considering removing the 3rd brake light entirely. Utah code seems to require two stop lamps and permits an optional third, so rather than relocating the third I am wondering if I can just remove it altogether without upsetting the Body Control Module.

I have been looking through a bunch of wiring diagrams, but can not find any mention of the 3rd brake light.

For example; the STOP-LAMPS-SYSTEM wiring diagram shows the left and right tail lights and the fault detection connections, but I am wondering how the 3rd stop lamp is integrated into the system.

Does anyone know what you might have to do to remove the 3rd stop lamp and convince the BCM that everything is still ok?

If so, how?

Thank you.

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[BullMoose1776]

I've unplugged mine while I was installing a bumper and tire carrier, and run the Jeep, driven the Jeep with no problems.

I always check it before I drove after I've been messing with it, and sometimes I have it plugged in wrong. Still no issues or problems.

Why do you feel the BCM will react if you unplug it?

 

[Mikeoso]

I thinkmthe third light is the unit at the far right of the module. I dont see a fault sensor there. It appeqrs to have connector sockets for the feed and ground. IF I'm reading that right, you should be able to just unplug it and see what happens.

 

[Yellow Cake Kid]

...Why do you feel the BCM will react if you unplug it?

The right and left stop lamps are shown in the wiring diagram as having a fault detect. Without having seen a wiring diagram for the third stop lamp I am left to speculate as to whether is does or does not have a fault detect connection.

That's why I was wondering if anyone knew what was going on with the connections.

Thank you!

 

[Yellow Cake Kid]

...the third light is the unit at the far right of the module...

The reason I didn't regard the item on the far right as the third stop lamp is that a "lamp" or "bulb" symbol is not shown, but after your mention of the possibility I have noticed the label "LAMP CHMSL" seems to suggest that it is for a lamp, and I suppose it is meant to represent the connector, as I think you have suggested.

If this is the 3rd lamp connector then the circuit it is refreshingly simple and should be easy to work with.

I wonder what CHMSL refers too?

Thank you!

 

[Gregj]

Center High Mount Stop Light

 

[Yellow Cake Kid]

Center High Mount Stop Light

Thank you for explaining. I was just coming back to post that I had looked up CHMSL and figured it out.

Now I am realizing that I may have kicked a hornets nest by posting "Utah code seems to require two stop lamps and permits an optional third" because even though that seems to be correct, the requirement for the third light is from federal code. There are plenty of examples of disagreement regarding which codes take precedence, so now I anticipate relocating it and not overthinking the details of the law, but am glad to understand that it should be an easy mod due to the simple wiring.

Thank you!

 

[Jeepney Johnny]

I haven't heard or read of any issues with malfunctioning or burned out LED 3rd brake lights causing any issues in cars. My Mother's old Cadillac had about 1/3 of its brake light LEDs out, and I didn't notice it affecting anything else.

I did have an old Camaro that exhibited a funny side effect with one of the 3rd brake light incandescent bulbs burned out: The cruise control wouldn't engage. Apparently, that electrical load was similar to when the brakes were being applied (I still don't completely understand it). As soon as I replaced that bulb, the cruise control started working again.

Years later, when the cruise control failed to engage, again. I checked the third brake light bulbs, and sure enough, the other bulb was burned out. When I replaced that one, the cruise control started working.

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