I've heard that some Subaru models have 3 clocks in the view of the driver, all on the CAN bus, one being the nav and another being a remote display for the nav, and one that's just there, of which none sync to each others. I've looked up how it happened, and discovered that to just to add insult to injury, at least one uses a uC that has RTC feature but no XTAL pin for 32.768kHz or one of any sane base 2 divisions and uses CPU clock of 15MHz or something for it, so it just drifts away.

I don't understand how Subaru stays in the business. Just how. It's a 4 digit time. Just broadcast it on CAN. Why not.

Also: a lot of these older, completely rectangular sat nav units actually follow what is colloqially known as "2DIN" standards. (cheap import Amazon)Aftermarket units are available and those can be swapped in with just a bit of work. That's what most people do when they have issues with the stock unit installed for their markets.

I had a luxury car from 2001 where the time could not be manually changed, only set to specific time zones. Of course, all the time zone rules had long diverged from its rule set, and it had to be changed four times a year to show the correct time.

This car also inexplicably forced you to manually choose a country, and then a time zone, despite having a GPS that already knew exactly where you were and already had chosen a previous time zone.

Carplay is nice but I would have settled for a non-luxury "clock set" button.

Awesome write up. Love it. And good thing you documented it, since in half a year you'll need it again.

My takeaway: You should have just gotten the SD card and trusted the previous owner. Sometimes "simple users" do know. ^^

Add to falsehoods programmers believe about time:

It can be changed without the SD card in the car radio.

My car came with a cheap low-quality aftermarket combination car stereo and GPS. It would only play music from discs (no USB support), didn’t even support variable bitrate MP3s, and the GPS didn’t know the car’s location half the time.

I finally replaced the head unit with a plastic bracket and a standard old school in-dash stereo system. Much nicer setup.

It’s the cars which can’t have their head unit replaced with a simple stereo which worry me.

I got a new samsung smart tv in April and never connected it to the internet. Just noticed (likely because if the DST change) that the date and time was all wrong when it turns on. Could not unnotice it. I was very pleasantly surprised I could manually set it and no internet was required. I expected to be annoyed at it forever or to go down a rabbit hole like this and fail.

My 2014 vehicle stopped updating it's time automatically a few years ago. I think some cellular technology was phased out or perhaps the cellular contract GM had for vehicle connectivity expired.

Either way I just manually set the time twice a year now - I guess I'm thankful it still has that option.

When I was playing around with the radio in my girlfriends vehicle there was no option to set manually on the clock screen. Seems like a pretty shortsighted move to not allow that.

A design rule for the display of any appliance with a clock: It must be possible to remove or hide the clock. I don’t need 10 devices to keep track of time for me.

As an Arizona resident, my recent Honda CRV's clock is off by an hour for half the year. Since usually the carplay display overrides the clock, it's no big deal, but it cracks me up that, despite being a professional programmer, I have yet to figure out how to set it correctly

I never understood why car companies don't put more effort and resources into their MMI systems. Audi is a big offender. I've never seen a more thoughtfully designed car with an MMI interface that's more frustrating and buggy.

For certain model years of nissan, there's this, btw

https://github.com/ea/bosch_headunit_root

If anyone feels like using that access to throw some tokens at various systems.

The revolution against shitty locked down software has begun and I LOVE IT

Okay, this was gratifying to read, but ... can't you wedge CarPlay onto this thing? I'd want a victory lap with root doing at least something. Bad apple on car boot, there's lots of options here!

I was just wondering the same thing for a 2013 Honda Civic - has the screen's (the "head unit"?) firmware been fully dumped and reverse engineered?

How realistic would it be to run fully custom firmware there, and even communicate over usb - for example, if I had a pi running in the car, and it used the usb connection to show things on the built-in display?

Pretty awesome write up to explain their journey in it all.

I suspect a bunch of car head units will face new problems in the spring when many Canadian provinces will no longer change their clocks. The units won't get updated DST rules.

I wonder how many systems have a good web browser embedded. Last time it was tried on a tesla, it could barely render a maplibre map.

The Web is a universal platform very capable in 2026.

Usually you can just get a modern OBDII scanner and set it via the diagnostics or hot functions.

Nice! Reminds me of my jailbreaking my car's computer to write a string to permanent memory

https://www.josephecombs.com/2026/09/08/coding-an-audi-batte...

not quite as difficult, but reminds me of a fix I found on reddit for Subaru Outback parasitic drain: https://www.reddit.com/r/subaru/comments/1evozzf/dead_batter...

Love it! Slightly more elegant than my solution: a piece of electrical tape over the clock.

an SD card requirement is crazy

The Renault Latitude is actually Samsung car right?

I wish someone would jailbreak the Nissan Leaf (MY2018) head unit. Every time I turn on the car, it shows a EULA asking if Nissan can please collect every detail of my car at all times and sell it to whoever asks.

Every. Time.

Even if I beat my head with hammers to think like a lawyer, I can't imagine how it would be necessary to ask constantly. Doesn't matter if I accept or decline, it still asks again.

Shitboxing ftw

Meanwhile me with shitbox

The French auto industry... has always been "Special"

8 inches or more of dashboard real estate to display "maps not found", "don't get distracted" warning, terms and conditions, and blinking "12:00". Having had rented a fair share of subcompact and compact cars in half dozen of countries, the car navigation was updated and working exactly only once.

> The system had DRM checks which rejected SD cards without the correct CID (a unique ID burned into the card) and files with signatures based on that specific CID, so I couldn't even copy the files to a blank SD card.

FWIW, there are grey market sites that will sell you an SD burned with a custom CID so you can clone an SD card with this kind of copy protection. It sounds like in this case maybe he could've gotten away with an empty maps card + menu definitions file.

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