Introduction

Why does this guide exist? On the most recent generation of Honda cars that came out in ~2023 and beyond like the 11th gen accord (2023+), 4th gen Honda Pilot (2023+), 6th gen Honda CR-V (2023+), there is a new harness needed to connect the comma to the car and code changes that are not necessarily in mainline which are needed to support these newer Hondas. It seems the comma team is working on a new revision of the whole harness setup so getting the Bosch-C harness into the public shop is not a high priority as of Q1 2024. As the Bosch-C harness is not sold in the comma shop we can create one by modifying the developer harness currently available in the comma shop. Once the harness is built, in order to run OpenPilot you should just need to install a fork.

I'm not sure if this is allowed but tomn8104 on discord is selling his old bosch-c connector as he made several while experimenting and creating this guide if you are interested in not having to go through all of this to make your own.

If you are new, below is a picture of what we are physically trying to do- we basically want to intercept the car’s signal, feed it to the comma, the comma will do some computations, and feed a new signal back to the car giving us advanced steering assist.

Parts

Part Name	Minimum Quantity	Estimated Cost	Notes
GT25-16DS-HU/R	1 (recommend 2)	$1.62	https://mou.sr/3Q61EQH This is the connector that takes the signal from the comma and feeds it back to your car. --- Consider ordering 2 in case you mess up
GT25H-2428SCF	8 (recommend 20)	$1.44 = .18*8	https://mou.sr/3vO9Gqu These are terminals for GT25-16DS-HU/R. You will need to crimp these onto your dev harness wires --- Consider ordering 2.5x as many in case you mess up- say 20
1376106-1	1 (recommend 2)	$1.79	https://mou.sr/4aWBgAt This is the connector that takes the signal from your car and feeds it to your comma. Note - 1376106-1 isn’t the official receptacle that honda uses to mate to the GT25-16DS-HU/R in the car- Honda uses something like a GT25-16DP-2.2V or GT25-16DP-2.2H. We determined 1376106-1 mates well in place of the GT25-16DP connectors and allows us to crimp whereas the GT25-16DP connectors require soldering. You can go the soldering route if you choose by ordering one of the aforementioned receptacles (The last letter is a form factor of whether the connector is at a right angle or straight. I would recommend the GT25-16DP-2.2V(56) from mouser if you do this because it seems the pins are spread out) but crimping is the standard for connections in cars to withstand vibrations and whatnot. If none of this makes sense, I would ignore it and order the 1376106-1. --- Consider ordering 2 in case you mess up
1376109-1	8 (recommend 20)	$2.24 = .28*8	https://mou.sr/3OKqzJ9 These are terminals for 1376106-1 you will need to crimp these onto your dev harness wires --- Consider ordering 2.5x as many in case you mess up- say 20
Optional - tesa 51608 tape		$7	Wrap your wires. There's multiple variants of tesa tape. 51608 is the fuzzy one and I would recommend that. There's another variant that is meant for hot stuff and gets black goo on everything.
Comma 3x		$1250	https://www.comma.ai/shop/comma-3x This comes with the comma, 2 mounts, and a OBD-C cable
Dev Harness		$200	https://www.comma.ai/shop/car-harness If you are clueless, you can just buy the dev harness. --- If you want to potentially save money you can order just the harness box https://www.comma.ai/shop/harness-box and build your own harness connector if you have 26 AWG wire (comma uses 26 AWG, I used 24 AWG), and order the molex connector (501646-2600 https://mou.sr/44sT9oM) + terminals (501647-1000 https://mou.sr/3xQaVG3) and make your own connector. You are saving money by not using the OBD port and that hardware. The OBD connection will allow your comma to go to sleep when you turn off your car rather than full powering off, so next time you turn on the car it'll wake up as opposed to doing a full boot. There's tradeoffs here in terms of battery drain. In my experience the comma boots pretty quickly and I prefer no OBD connection. With the OBD connection, the comma will automatically go to a deeper sleep after a set time period with the car off.
Wire strippers		$3-$15	The dev harness uses 26 AWG but you don’t need strippers that are exactly 26 AWG, so long as you can get the sheath off without damaging the wire you should be good. A lot of pliers have an edge you can wire strip with though they arent as easy to use. I personally use v notch wire strippers and set the stop screw at the correct diameter https://www.harborfreight.com/electrical/electrician-s-tools/wire-strippers-crimpers/5-in-v-notch-wire-stripper-59713.html If you are stripping a lot of wires, the auto tensioning wire strippers are nice. Sometimes they nick some strands. I made my own harness with 24 AWG as a note https://www.harborfreight.com/electrical/electrician-s-tools/wire-strippers-crimpers/pistol-grip-self-adjusting-wire-stripper-and-cutter-59729.html
Crimper		$20	For a proper connection you should use a real crimper to get the metals to basically cold weld together, otherwise you might have a loose connection. I ordered https://www.amazon.com/dp/B08DLHKKPH off of amazon, to be determined if they are good. Again the comma uses 26 AWG wire. Some people have used pliers, I can’t officially recommend regular old pliers like needle nose pliers but they might do the job. If you have a tool library look there so you don’t have to buy a tool to do a job once and never again.
Optional - trim removal tools		$5	I used a screwdriver, if you aren't careful you can scratch your camera shroud https://www.harborfreight.com/trim-and-molding-tool-set-5-piece-64126.html

Wiring diagram

Wiring is in the diagram below - TODO is to update the diagram with the new connector. For now please ignore the top right 5016461200 connector - you do not have that connector and it shouldn’t make sense to you as we do not have access to comma’s adapter boards- the original prototypes did weird stuff basically converting a 12 pin connector to a 16 pin connector and crossing a bunch of the pins.

You should first add the GT25H-2024SCF terminals to the wires that will be wired up the GT25-16DS-HU/R. Then put those wires in the connector and lock them in with the little retainer tab on the connector. Insert the folded side of the crimp facing inwards into the middle of the connector like this video https://www.youtube.com/shorts/EgmIeZp_uYE.

On the remaining wires, crimp on the 1376109-1 terminals. To determine what slot in the 1376106-1 connector we should place these, compare the (already wired) GT25-16DS-HU/R and (currently unwired) 1376106-1 to each other. Look at the colors and mirror what would happen if the same color wire on the GT25 went through to the 1376106-1 and wire in the terminals. Following the logic from the first diagram in this document, you are basically intercepting the signal from the car (The car has it’s own GT25-16DS-HU/R connector inside it), to the comma’s new 1376106-1 connector, to the comma 3x via the dev harness, to your comma’s new GT25-16DS-HU/R via the dev harness, and back to the car via your new GT25-16DS-HU/R attached to the comma.

Installation

We need to remove the shroud for our camera and wire in our comma. Here's a video pulling apart the shroud and talking about replacing the connector for an already installed comma https://www.youtube.com/watch?v=Csj02NEtpkY A text and image explanation follows.

The hardest part to remove is the first black cover. Here's a picture of the tabs. I pull down on the left half, insert a screwdriver (you should probably use a nylon car trim removal tool) and turn it right in the middle to pop the first tab, then I pull the right half outwards to the passenger side of the car, sliding the cover out by hand.

Here's where I put my screwdriver to pry down the last grey cover. Note the airbag light is attached so don't pull the cover fully off without disconnecting the wire first. You will need to pop two tabs, one on the left and one on the right. In the second picture you can see the two yellow tabs, which is where you will line up your removal tool.

Once your shroud is off here is the comma guide. https://www.youtube.com/watch?v=FV7_Su4xbzs

Note- you actually don’t need the rj45 cable/to use your OBD port. Using your OBD port ensures the comma goes into sleep mode and can turn back on quickly after turning off your car as the OBD is essentially always on. Relying on no rj45 means your comma needs to do a full boot basically each time you want to use it. There’s tradeoffs here- one might drain your battery, the other might be annoying. It’s your preference.

Here’s a sample picture of the harness connected to the car. The car’s connector is at the very top and you need to reach above the heat sink and between the visor to unclip the connector. It will need to be unclipped then pulled out. The heat sink may be hot if you were just driving so be careful. Do not run the comma with the exposed wires dangling as you risk shorting them.

You may be able to tuck your harness into the headliner, it's a tight fit, I created a second harness with short wires to the white receptable and longer to the GT plug which allowed it to fit into the pocket. I tesa taped the box and connectors to prevent rattling. The OBD-c cable can be tucked along the left side where the rear view mirror connector is guided and fed out the black two part shroud at the bottom. Optionally you can drill a hole in the back of the shroud to go directly to the comma without having to loop back

The longest step is waiting for the mount to cure. Comma recommends 2 days. Here’s a chart from 3m on strength to cure time. https://www.3m.com/3M/en_US/bonding-and-assembly-us/resources/full-story/?storyid=b3996cbd-9954-455f-8e72-88e452ca38c0#

Once the mount is cured, plug in everything and supply the URL for installation. You must have a stable wifi connection- without a stable connection and stable power supply your comma might keep rebooting. If your connection and power is stable but the comma is still rebooting, you may need to install stock openpilot first (openpilot.comma.ai) before installing the branch, especially if you have a new Comma3X and have never done so before.

Current branch for 2023 Honda Accord: installer.comma.ai/vanillagorillaa/23_accord

Current branch for 2023 Pilot : installer.comma.ai/vanillagorillaa/Pilot_2023

Thanks to the community

• Babyhamsta - Rush ordering parts, building the new prototype, and being the first to get OP running on their 11th gen honda accord
• Kevmaninc - Providing info to reverse engineer and improve the bosch c harness
• Vanillagorillaa - Got open pilot working for this generation of bosch c honda cars https://github.com/commaai/opendbc/pull/999
• Foodbandlt - Technical knowledge and support on how to build this harness/debug issues
• Natez - Wizardry in discovering a 1376106-1 connects to a GT25-16DS-HU/R which allows us to make this harness without soldering
• Tomn - this guide