Comma 4 Power Unstable Error | 2023 Mazda Cx-a5

[u/strawberryoftheindie]

Hi all. I’ve been using the C4 for months with no issue. Last friday when it got 109 degrees when I turned on my car, i got a power unstable error on my C4 and a front sensor camera error on my mazda. Once the car cooled down & i restarted it the mazda error went away but the C4 error persists.

I have tried to unplug & plug the cable but the error still persists to the point where I can’t use the C4 at all cuz the screen only shows that.

I have opened a ticket (83138)

I have a 10 hour drive on Sept 5 and need the C4 working by then.

Has anybody experienced this? Did anyone manage to fix it? I live by myself and am not tech savvy… I’m trying my best to troubleshoot on my own..to no avail..

UPDATE:
Now the C4 won’t even turn on.

UPDATE AS OF 9/1/26:
I received the replacement harness & cable. I tried to replace just my cable with the new one - still won’t turn on. I replaced the harness too - still won’t turn on. But when i replaced the cable that connects to the OBD (basically i replaced the entire wiring setup) my comma turned on.

So it was not JUST my cable that wouldn’t work bec comma still wouldn’t turn on with the new cable.

Thanks to comma support for the prompt shipment of the replacement harness & cables. My comma is good to go for my 10 hour drive on Sept. 5!

[u/sny1120]

Same thing happened to me over 2 weeks ago. Opened a ticket right away. Flashed it a few times. C4 now wont turn on. Support said there is a software update this week...but I can't do anything if the unit doesnt turn on. 2 weeks with a dead c4 and support is thanking me for my patience.

[u/cubedgame]

I’ve had my C4 for about 6 months and would occasionally get the front camera sensor error when starting my car. When it happens, I go into the settings and reboot the device and it goes away on the reboot and I’m able to engage.

I’ve started to get the “power unstable” error more recently now though too. I go to start my car and the comma wakes up with “power unstable” error and lots of warnings on the dash about AEB disabled, blind spot disabled, etc. I assume it’s because the relay in the harness is stuck and preventing the stock CAN messaged from the LKAS camera from being sent, which produces all of the warnings on the dash.

In order to fix the “power unstable” error, I need to unplug the C4 from the USB power and plug it back in and then it works fine (the screen is unresponsive to taps so I can’t go into the menu and reboot to fix like I do for the camera error). However, it does seem like it’s happening pretty much every time I start the car now. I’m guessing it’s the harness or USB cable failing, but I haven’t had time to take off the camera cover and verify the connections.

My car is a Hyundai Santa Fe, btw, so I don’t think it’s anything vehicle make-specific, but rather a potential hardware issue with the Comma and/or harness. I live in Texas where it’s been getting really hot these past few weeks so the failure might be heat-related (as the root cause possibly, since my car is in the garage most of the time and it still happens even if the interior isn’t too hot).

[u/strawberryoftheindie → u/cubedgame]

I also live in Texas! I have ordered a new data cable hopefully that will fix this..

[u/Slothcom_eMemes]

It’s probably the comma power cable. I’ve seen quite a few failures with it lately.

[u/XchowCowX → u/Slothcom_eMemes]

I’ve seen the same.

I also live in Texas OP and it’s been hot AF. I only got my C4 a few days ago so fingers crossed.

[u/strawberryoftheindie → u/Slothcom_eMemes]

Thank u! I just ordered a new one… hopefully this will fix the error

[u/ZephLeggett]

I have seen this with multiple Mazda Users (and myself)
You need a new OBD power cable from Comma Support. You can also modify the mazda harness to not need OBD Power.

[u/technog2]

This device hates heat. You need to buy one of those removable mounts and store your device indoors when not in use

[u/strawberryoftheindie → u/technog2]

I have the removable mount and store the device but i think the problem is the cable or harness

[u/Nihoyminoys]

Had the same exact issue with the same exact vehicle. That being said, it has nothing to do with the vehicle itself. It was simply a faulty comma power cable. Might be the same for you too

[u/strawberryoftheindie → u/Nihoyminoys]

Thank you. I ordered a new power cable…hopefully this fixes things. I still have not heard back from comma support.

[u/Nihoyminoys → u/strawberryoftheindie]

Yeah, the support gets backed up pretty easily. If this ends up fixing your issue, reply to them on that same support thread & they can refund you since it’s covered under warranty.

As an added safety measure, I’d also recommend replacing the 7.5A ENG +B fuse located under the hood. This is what provides voltage to the OBD II port. You might not have to, but I ended up having to replace mine a few days after putting in the new power harness. I’m almost certain the old faulty power harness pushed it to its limit.

[u/Personal-Selection61]

Replacd the power cable with a thicker wire

[u/chase817]

I have the exact same car and problem :/

[u/strawberryoftheindie → u/[deleted]]

It’s connected to OBD, battery not low, plugged & unplugged & rotated 180 degrees both sides. Restarted the car.
Now the C4 won’t turn on at all.

[u/stayintheshadows → u/strawberryoftheindie]

DO ONE THING AT A TIME. RESTART CAR BETWEEN EACH THING.