Comma AI self driver assistant

[Ajzride]

Hey all, I've had my 3x installed and running with no issues on my '23 XLT for the past year with no issues, until the past few weeks. I started getting a "Canbus disconnected. Likely faulty cable error" message on the comma sporadically, and the truck would throw camera and parking sensor errors at the same time. I could usually disconnect my comma (I have a 3D printer and printed a quick-disconnect mount similar to the one Ajzride has designed), then reconnect it, and it would usually come back up and work fine. But, recently, that has not been the case.
I have a Ford Q4 harness that I modified (cut and soldered in an extension). I assumed it was a bad solder joint because when I disconnected the comma, all the errors the truck was throwing went away.
I've taken the harness out, desoldered/resoldered all the connections I made with the extension, to no avail. I'm at my wits' end on this one. I'm not sure what to do at this point other than order a new harness and adapter to try it.
I have probed all the pins on the harness I have, and I have good continuity across all conductors, including the pairs with resistors to prevent start-up errors.
I have also tried swapping out all the USB cables from the harness box to the comma and eliminating all adapters to no avail.
I'm at a point now where the truck is throwing errors when the harness is plugged in, regardless of whether or not the comma is connected on the other end. The only thing I can think to try at this point is to order a new Q4 harness and the lightning coupler to try that combo.
Any help on this would be greatly appreciated.

It could be the actual harness box. Based on the time frame, you probably have the old style harness box with a mechanical relay. Honestly the best path forwards is to order a new Q4 harness kit and the coupler. This will get you the new style harness box which is solid state instead of mechanical, along with the automotive grade resistor coupler that Uncle Tony designed, which is far more robust and much more balanced for the system than the resistor design I initially made a video on installing.

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[DIEProphezeiung]

Honestly the best path forwards is to order a new Q4 harness kit and the coupler.

Ordered. I'll update here when they come in on whether it fixed the issue or not.
I didn't consider the harness box itself going out. Now I'm gonna pop that thing open when I get back home and start probing around.

 

[chriserx]

Hey all, I've had my 3x installed and running with no issues on my '23 XLT for the past year with no issues, until the past few weeks. I started getting a "Canbus disconnected. Likely faulty cable error" message on the comma sporadically, and the truck would throw camera and parking sensor errors at the same time. I could usually disconnect my comma (I have a 3D printer and printed a quick-disconnect mount similar to the one Ajzride has designed), then reconnect it, and it would usually come back up and work fine. But, recently, that has not been the case.
I have a Ford Q4 harness that I modified (cut and soldered in an extension). I assumed it was a bad solder joint because when I disconnected the comma, all the errors the truck was throwing went away.
I've taken the harness out, desoldered/resoldered all the connections I made with the extension, to no avail. I'm at my wits' end on this one. I'm not sure what to do at this point other than order a new harness and adapter to try it.
I have probed all the pins on the harness I have, and I have good continuity across all conductors, including the pairs with resistors to prevent start-up errors.
I have also tried swapping out all the USB cables from the harness box to the comma and eliminating all adapters to no avail.
I'm at a point now where the truck is throwing errors when the harness is plugged in, regardless of whether or not the comma is connected on the other end. The only thing I can think to try at this point is to order a new Q4 harness and the lightning coupler to try that combo.
Any help on this would be greatly appreciated.

So, I've noticed it too, and from what it looks like to me is the Comma doesn't receive the truck off signal, when the truck is turned on again it gives the error, rebooting while in park seems to fix it, if not it throws another CAN bus error. This is just my experience so far and it's not definitive until I can find if and where they keep the communication logs on the comma.

 

[DIEProphezeiung]

So, I've noticed it too, and from what it looks like to me is the Comma doesn't receive the truck off signal, when the truck is turned on again it gives the error, rebooting while in park seems to fix it, if not it throws another CAN bus error. This is just my experience so far and it's not definitive until I can find if and where they keep the communication logs on the comma.

Interesting. I hadn't considered whether the power on/off sequence would make a difference. I don't have any particular consistency on how I connect/disconnect my comma. I always remove it from the mount and store it in the glovebox when the truck is parked. But while troubleshooting recently, I did try connecting it before powering on the truck and power cycling the comma while in park. None have helped with recent issues.
In the past, when I was able to power cycle the comma and have it come back working fine, I usually did so while driving.

 

[chriserx]

I literally just remote started my truck, walk out and could see the comma saying it was stopped for 300ish minutes, was going to take a pic for this thread, opened the door and it reset to 0

 

[Ajzride]

I literally just remote started my truck, walk out and could see the comma saying it was stopped for 300ish minutes, was going to take a pic for this thread, opened the door and it reset to 0

That is a known quirk with the stopped timer. It keeps track while the vehicle is off, even overnight.

 

[chriserx]

That is a known quirk with the stopped timer. It keeps track while the vehicle is off, even overnight.

My suspicions of the CAN bus issue predates my use of the stop timer, you wouldnt happen to know where the logs are kept would you? All i've found so far is the video files and the car fingerprints to manually add the 2025 lightning. Any clues would be helpful.

 

[UncleTony]

My suspicions of the CAN bus issue predates my use of the stop timer, you wouldnt happen to know where the logs are kept would you? All i've found so far is the video files and the car fingerprints to manually add the 2025 lightning. Any clues would be helpful.

Does the comma go offroad when the truck is turned off? Or does the road cam stay on the screen?

 

[chriserx]

Does the comma go offroad when the truck is turned off? Or does the road cam stay on the screen?

Road cam stays on the screen, I've caught it red handed twice just because I happened to be walking by the truck with it off. Could potentially be a bad cable, I am using the stock comma cable, and it did give me problems initially.

 

[UncleTony]

Road cam stays on the screen, I've caught it red handed twice just because I happened to be walking by the truck with it off. Could potentially be a bad cable, I am using the stock comma cable, and it did give me problems initially.

If the road cam stays on the screen, it is likely falsely detecting ignition like you are thinking. My first guess would be your harness or harness box is having an issue.

 

[Ajzride]

If the road cam stays on the screen, it is likely falsely detecting ignition like you are thinking. My first guess would be your harness or harness box is having an issue.

correct. I misunderstood the initial comment.when I had problems with the device not shutting off it was my harness box.

 

[chriserx]

If the road cam stays on the screen, it is likely falsely detecting ignition like you are thinking. My first guess would be your harness or harness box is having an issue.

Either direction, ignition on or off, i want to narrow it down, I'll keep looking for any logs I can, are there any SSH commands to view the CAN bus live? My gut says probably not since the traffic volume is likely pretty high but figure I'd ask anyway

 

[UncleTony]

Either direction, ignition on or off, i want to narrow it down, I'll keep looking for any logs I can, are there any SSH commands to view the CAN bus live? My gut says probably not since the traffic volume is likely pretty high but figure I'd ask anyway

You would need to setup an open pilot dev environment to view the logs.

This can help you get started.

https://github.com/sunnypilot/sunnypilot/tree/master/tools

Not to discourage you from going down that route, but its only $100 for a new harness and you can return it within 30 days if its not your issue.

 

[chriserx]

You would need to setup an open pilot dev environment to view the logs.

This can help you get started.

https://github.com/sunnypilot/sunnypilot/tree/master/tools

Not to discourage you from going down that route, but its only $100 for a new harness and you can return it within 30 days if its not your issue.

I've already enabled ADB and SSH even though I don't particularly care for the way they do SSH key exchange. I'm sure it's fine though. On bp-4.0 I wanted to see if experimental mode had improved any since installing on the Corolla so I added the 2025 to the fingerprint list. Didn't care for it so turned it back off. bp-5.0 is looking pretty good so far though.

 

[kzoojason76]

https://bluepilot.dev/2025/10/28/bluepilot-5-0-beta-release/

Working great so far. I noticed that 5.0 seems to have corrected my "ping-pong" in the lane that I was having with 4.0.

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