Car manufacturers aren’t required to document how to repair “infotainment centers” because they aren’t critical to the operation of a car. Making them more useful might require a car manufacturer to spend more money by allowing more requirements to be imposed upon them.

They don’t want to maintain the software for it.

Also, they simply don’t want you to know. Especially if the whole setup is already a patchwork of sensors that barely work together in the first place. It might cause unnecessary questions, concerns or even liabilities.

A lot of it is useless anyway as long as the car is not broken, and if it is broken, the sensor might be broken too. It’s meant for diagnostics only.

What I’ve learned with 15 years in the DIY repair sphere is that (obviously to me) the codes don’t tell you what’s at fault, only what’s not reading correctly and (to my surprise) the general public will just replace what the code says is off. A MAF code doesn’t tell you if it’s the sensor, the wiring, or the PCM.

While I’d certainly appreciate a simple code readout because I’m pretty knowledgeable about which are actually concerning this moment vs this year vs never, diagnosis typically takes more equipment and time. The cost and hassle of the reader is negligible in the repair. I use a Bluetooth dongle and Torque app to read all kinds of stats when diagnosing. An integrated interface would be convenient in some ways, but the portability of a phone/tablet probably has an equal amount of convenience once hard diag is needed

The same reason they won’t let you buy the dealership scan software for under 10k. Almost every maker has an in house scanner and due to standards they only need to provide certain data to non dealer level tools and I believe the standard only exists for gas powered vehicles that need to provide OBD2 data. Plenty of makers (BMW is horrible about this) stuff away data where a normal obd scanner just won’t access and it’s gotten much worse with the overuse of CANBus (I sure love when my trunk lid sensor prevents my fucking car from starting).

Thats where your snapon and other third party scanners start bringing a gap, but even those are extremely pricey and need to be updated constantly and even those usually won’t do EVERYTHING.

Fwiw the cheapest and best way I’ve found is basically to pirate the dealer software and get a compatible knockoff scanner (vxdiag for example). I have Ford IDS and a couple others this way but assume that the software is gonna install something malicious and dedicate an old Thinkpad or something to it.

Depending on the age of your vehicle something like Torque Pro is extremely useful. I have mine monitoring transmission temp, long and short term fuel trims, O2 sensor signals, voltage, mass air speed, intake temp. It’s more than enough data to see something coming long before it becomes an issue.

As someone pointed out on the comment, one of the reason is Money, the other one is safety and security based on Vehicle manufacturer claim.

Yet, nobody can stop you to sniff and monitor your own car CAN/OBD2 interface using as simple as cheap microcontroller and compatible OBD2 interface kit (e.g CAN Transceiver/Controller kit).

EDIT: So far this curated list helpful to me for CAN bus based protocol.

As other mentioned cheap ODB2 readers, but some brands offer a lot of diagnostic data over the infotainment system, they just won’t display them to you - for BMW I use AAIdrive (is foss, github/AAIdrive) and it displays some of the data on the main screen without a physical ODB2 reader inserted.
(And ofc custom navigation, VLC, etc)

We could have had readable diagnostics since they started showing multiple items on the in-dash LCDs. It’s always money.

I’m not aware of any car manufacturers selling their own diagnostic ASICs, so it’s not an extra margin to squeeze afaik…

What? The errors are intentionally vague so the drivers are forced to go to a dealer, giving them a chance to lie and pretend that’s something very serious and very expensive, while all they’re going to do is a reseat of a cable and a error reset

Btw Car scanner supports showing obd data on Android auto. It’s a game changer for hypermilers

Money

I don’t know if that’s the reason but it probably is

The sad answer is that those displays exist to cut costs, not to make your ownership experience better.

Also the dealers want you to come to them for that CEL, and the companies don’t want to piss off the dealers.

Some cars do! Mine shows diagnostic info for the can bus and GPS by holding down a “secret” button combination. I’m sure other manufacturers do that too.