[Robaroni]

You are absolutely correct. This thread was about modifying the lights and I had no reason to post anything else. how to modify the lights is not a matter of opinion. My apologies.

No problem and no hard feelings,
Best to you,
Rob

 

[TennErnieChevy]

No problem and no hard feelings,
Best to you,
Rob

And to you as well.
Philip

 

[maximus]

For those interested who feel this mod is beyond their abilities I could design a system that does not require cutting existing wires, it does require circuitry though, if there is enough response I will be happy to post the schematics and procedure here. My intent with all of this is to genuinely help people and make them safer.

Yes, I would be interested. I am not too handy, and very weary to cut open wires in an all electric cal. 2 years from now, I don't want to be wrangling with GM/Dealer that it was NOT this mod that caused some random failure.

Would like an option , where I can 'undo' the mod and take it in... (shhh)

When we took delivery, my wife drove behind me and we checked. As mentioned in other posts, if the headlights are not on, only the 2 lower lights light up when accelerator is released. With headlight on, there were 5 lights that came on. She thought it was 'ok' to just have two, but 'better' to have all 5.

 

[Leather Bear]

...if the headlights are not on, only the 2 lower lights light up when accelerator is released. With headlight on, there were 5 lights that came on. She thought it was 'ok' to just have two, but 'better' to have all 5.

For 2022 and 2023 models, each of the rear light assemblies have a different function (or functions, re the lights in the bumper). Starting from the top:

• Upper (above the back window): this is the CHMSL (Center High Mount Stop Light). It turns on at high intensity whenever the brake pedal is depressed, the “extra regen” paddle behind the steering wheel is pulled, or (if One Pedal Mode is active) the driver backs off the accelerator sufficiently for OPM to mimic depressing the brake pedal.
• Middle (on the left and right side of the rear hatch on both EV and EUV and in the corners of the rear fenders on the EUV): these are the taillights. These turn on at low intensity whenever the headlights (or parking lights) are on. They aren’t activated with any other functions.
• Lower (on the left and right side of the rear bumper): at high intensity these are brake lights (same functions as the CHMSL above), also for turn signals and emergency flashers. These lights will also turn on at low intensity (on the EV; I haven’t checked this on an EUV) as substitute taillights if the rear hatch is opened.

If the accelerator pedal is released, none of the rear lights should turn at all on unless OPM is activated; both the CHMSL and the “lower” bumper lights should turn on if in OPM. If the headlights are on, the “middle” taillights remain on regardless of the accelerator being depressed or released.

 

[Coastal_Cruiser]

howto

Yeah, a plug-n-play solution would be great.

Barring that, I'm just going to keep my fingers crossed that I don't get rear-ended because someone didn't see the low-mounted brake lights.

For those interested who feel this mod is beyond their abilities I could design a system that does not require cutting existing wires, it does require circuitry though, if there is enough response I will be happy to post the schematics and procedure here. My intent with all of this is to genuinely help people and make them safer.

Yes, I would be interested. I am not too handy, and very weary to cut open wires in an all electric cal. 2 years from now, I don't want to be wrangling with GM/Dealer that it was NOT this mod that caused some random failure.

Would like an option , where I can 'undo' the mod and take it in... (shhh)

When we took delivery, my wife drove behind me and we checked. As mentioned in other posts, if the headlights are not on, only the 2 lower lights light up when accelerator is released. With headlight on, there were 5 lights that came on. She thought it was 'ok' to just have two, but 'better' to have all 5.

As I move closer to making the mod, I am thinking of a way to avoid hacking into the leads feeding the upper brake light. @Robaroni, or anyone whose been in there, I was thinking of an additional coupler that could be inserted and have the tap for the brake lights feed from that. In other words, uncouple the existing OEM coupler that feeds the upper brake lights, insert the "man in the middle" coupler between the OEM coupler. Each side of the OEM coupler then connects to the additional coupler.

Now you have a clean tap that can be undone if need be and leave no trace. And while not pure plug and play, much easier for those sans soldering skills. The question is, does such an off-the-shelf part exist (a T tap ideally), even if the purchaser would have to attach the two wires to it that will feed the new brake light.

Capiche?

 

[Cruzincat50]

howto
With Robaroni's mod, the only concern I might have is the possibility that the fuse would blow on the circuits that power the existing brake light system. It would be highly unlikely, but it can't be ruled out. That begs the question, if the fuse blows, does the vehicle have monitoring that would give some indication that you now have even less visibility, and you need to get off the road and get it fixed? If someone does test this, by removing the fuse that might blow, can you also test the effects on the four way flasher?

Maybe it would be prudent to add an inline fuse holder and add a fuse of the appropriate size, that would trip before the main fuse would. It would be installed on the wire leading to the new led lights.

 

[GB74]

howto
Of the 9 Fuses that feed into the Body Control Module, the Instrument Panel Fuse F09 is shown on Power Distribution Diagrams to be for:

F09 15A Body Control Module 1 (BCM-) - X2, pin 1
--> Power Moding --> K114B Hybrid/EV Powertrain Control Module 2
--> KR73A Ignition Main Relay 1
--> KR73B Ignition Main Relay 2
--> K33 HVAC Control Module - IGN
--> S26 Hazard Warning Switch - Indicator Light
--> E7 License Plate Lamp
--> E6 Center High Mounted Stop Lamp

Since the BCM is mostly all flat pack ICs that contain some kind of MOSFET, it's the MOSFETs that are feeding the circuits like the CHMSL, not just one individual fuse per BCM output.

Example of a Chevy Sonic BCM PN 13506936, looks like it has 2 Relays and many ICs/MOSFETs:
I don't have a photo of the Bolt's BCM, but most likely similar.

 

[Cruzincat50]

howto

Of the 9 Fuses that feed into the Body Control Module, the Instrument Panel Fuse F09 is shown on Power Distribution Diagrams to be for:

F09 15A Body Control Module 1 (BCM-) - X2, pin 1
--> Power Moding --> K114B Hybrid/EV Powertrain Control Module 2
--> KR73A Ignition Main Relay 1
--> KR73B Ignition Main Relay 2....
....--> E6 Center High Mounted Stop Lamp....

To me, that sounds like it would be extremely noticeable if the fuse F09 blows. Now, however, I am wondering how much a BCM costs to replace, since its outputs do not seem to be protected with fuses. Although the items in the following photo look like fuses, but they would probably not be replaceable at the dealership level.

 

[KrustyKush]

So, Robaroni, you cannot produce ANY verifiable evidence of crashes caused by this supposed defect of design.

Not a single incident. Not even your own.

Meantime, NHTSA appears not to be investigating.

Remember how many battery fires caused a massive recall? A handful. And you claim there are reports of rear-enders all over. Can anyone truly believe that if rear-enders were epidemic the NHTSA would not have already demanded a redesign?

I’m proud of you, Robaroni, for being the tip of the spear on this. I hope GM doesn’t take offense at your evidence-free public defaming of their stuff.

 

[Coastal_Cruiser]

OK, are you done now? We got the point. Why don't you run along now and pick another forum to heckle. Or do we have to put you on ignore?

 

[KP80]

howto

...
Although the items in the following photo look like fuses, but they would probably not be replaceable at the dealership level.
View attachment 56677

Those are surface mount capacitors, there likely aren't any fuses on that board that are easily replaced.

As far as the topic at hand, I have to say I think someone would see a lot of interest if they whipped up a pre-made wiring harness to handle adding additional brake lights like this or even a plug and play solution to use the middle running lights as brake lights as well. Most of the cost would be in getting the same plugs GM uses for the wiring in the back, but that could be a slick project. You could even make the cable dual purpose where the lighting output comes off a little pigtail to run extra lights, or with a jumper it simply runs the middle lights for brakes. Just spit balling some ideas here in case someone has the time and effort available.

 

[TennErnieChevy]

So, Robaroni, you cannot produce ANY verifiable evidence of crashes caused by this supposed defect of design.

Not a single incident. Not even your own.

Meantime, NHTSA appears not to be investigating.

Remember how many battery fires caused a massive recall? A handful. And you claim there are reports of rear-enders all over. Can anyone truly believe that if rear-enders were epidemic the NHTSA would not have already demanded a redesign?

I’m proud of you, Robaroni, for being the tip of the spear on this. I hope GM doesn’t take offense at your evidence-free public defaming of their stuff.

Krusty, as one who agrees with you, I am asking you to not post your feeling on the subject in the thread. It took a minute or two for me to understand that this thread is about HOW to modify the lights. It is not about the NEED to modify the lights. I offered my apologies for not seeing that sooner and butting in.

Thanks,
Philip

 

[KrustyKush]

Thank you, Philip, for your reasonable ask.

I disagree. The OP and a few others have turned this into a modification party. They should beware the unintended consequence.

It may seem simple to do this, and maybe it is, but I have seen really simple-seeming mods turn into nightmares.

Still, their property, their consequence. All I propose is to question the need. I ask for evidence, OP has only his gut feeling. That isn’t enough.

 

[no-gas]

Those are surface mount capacitors, there likely aren't any fuses on that board that are easily replaced.

As far as the topic at hand, I have to say I think someone would see a lot of interest if they whipped up a pre-made wiring harness to handle adding additional brake lights like this or even a plug and play solution to use the middle running lights as brake lights as well. Most of the cost would be in getting the same plugs GM uses for the wiring in the back, but that could be a slick project. You could even make the cable dual purpose where the lighting output comes off a little pigtail to run extra lights, or with a jumper it simply runs the middle lights for brakes. Just spit balling some ideas here in case someone has the time and effort available.

Agree. I hate cutting or splicing wires. I would prefer simply unplugging the connectors, plugging new connectors in that will hook up to whatever lights or devices. This way, it will be super easy to rollback the changes to stock. I

I took pics of the CHMSL connector but I cannot find the part# or name for it.

 

[KrustyKush]

OK, are you done now? We got the point. Why don't you run along now and pick another forum to heckle. Or do we have to put you on ignore?

Thank you, Coastal. I do not fear your ignorance. Ignore as you must.

Why don’t you run along now and start slicing into your Bolt’s wiring. Good Luck!

 

[Coastal_Cruiser]

howto

Agree. I hate cutting or splicing wires. I would prefer simply unplugging the connectors, plugging new connectors in that will hook up to whatever lights or devices. This way, it will be super easy to rollback the changes to stock. I

I took pics of the CHMSL connector but I cannot find the part# or name for it.

More spit balling... another approach might be to cut off the two connectors and reattach the wires to a T-connector that sort of resembles the OEM one. Any similar sized 2-wire T-connector that handles that gauge of wire may do.

Question: do you think there is enough slack in the existing harness to cut off the connectors and attach a new connector?

 

[no-gas]

howto
Good idea, @Coastal_Cruiser I can't remember how much slack there is. I guess, there should be enough to make it work. Here is a pic of the brake light connector.

This is the other one.

 

[Coastal_Cruiser]

howto

This is the other one.
View attachment 56694

When you "the other one" are you referring to the connector for the brake lights on the bumper?

 

[no-gas]

howto
No, this one is right next to the CHMSL connection. I pulled that pic from this below thread. (Sorry hijack your thread, @Robaroni )

2022 and 2023 EUV Tail Light Mod

I mod my 2023 Bolt EUV LT tail light (on lift gate only), i follow somebody else post but instead of diodes i use: " Diode Dynamics" Automotive PWM Dimmer With Bypass, i got from Amazon, its sold by pear and i use each dimmer for left and right tail lite on lift gate. easy job if you have hands...

www.chevybolt.org

 

[GregBrew]

Yeah, a plug-n-play solution would be great.

Barring that, I'm just going to keep my fingers crossed that I don't get rear-ended because someone didn't see the low-mounted brake lights.

Or the high-mounted third brake light.