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When I bought my current car, it came with an owners manual--for free!! I can grab any data I want from the OBD port. The hardware was cheap, the software to u

When I bought my current car, it came with an owners manual--for free!! I can grab any data I want from the OBD port. The hardware was cheap, the software to use it is, again, free. I'm not excited about this brave new world where you have to pay a subscription fee to plug a cable into a device you own and interact with it, and even less excited there are people here defending the idea.

loopies 5d ago
What you want is the service manual. Owner manual should be implicit. OBD port can work for some cars, for some of the data. But other cars do have specialized gear they require to either access either reset some stuff in some of the car's computers.
- somehnguy 5d ago
  Yeah the owners and service manuals are two very very different things. You won't be performing much maintenance with the owners manual besides the absolute basics, like checking your oil. The cheap OBD2 readers lack the vast majority of data and tools you would want to use for service as well. There are aftermarket options but most manufacturers want you to subscribe to their service tools - often charged per monthly plus an additional a fee per VIN it touches. These cost in the hundreds to thousands. It can be pretty frustrating as a shadetree mechanic.
  - lazide 5d ago
    Notably, some vehicles like the Toyota Highlander you can’t even figure out when you need to change the spark plugs, let alone what kind of spark plugs you need from the owners manual. Theoretically, they are to be replaced at 120k miles (!!) but they won’t even tell you that in the owners manual. Insane.
    - somehnguy 5d ago
      It is, yeah. The owners manual for my current vehicle seems to mostly contain walkthroughs about the infotainment and other tech features. The section related to maintenance is tiny in comparison. You're probably aware of this already but luckily a lot of service manuals can be found online in PDF form. Somewhat related but I was going through an older relatives belongings not too long ago to help cleanup and found a bunch of old manuals for various household things. The detail included in them was beautiful to see - full wiring diagrams, mechanical diagrams, etc.
      - skeeter2020 5d ago
        >> You're probably aware of this already but luckily a lot of service manuals can be found online in PDF form. Not official ones for John Deere tractors unless they were leaked from authorized service agents!
        BenjiWiebe 5d ago
        And those get taken down when JD finds them.
    - sokoloff 5d ago
      The change interval is in the Warranty and Maintenance Guide, not in the main owner’s manual. (This is still part of the in-glovebox manuals, not a service-center manual.) One example: https://assets.sia.toyota.com/publications/en/omms-s/T-MMS-17Highlander/pdf/T-MMS-17Highlander.pdf https://assets.sia.toyota.com/publications/en/omms-s/T-MMS-1...
- 27183 5d ago
  Reading codes is only part of it. For the last quarter century or so (some manufacturers more than others) if you replace certain components (radio, any computer module) you need to update the ECU to recognize the new component. This requires proprietary software and in many cases proprietary hardware as well. These "features" are marketed as an "anti-theft" mechanism. This renders some repairs basically impossible for the end user to perform. The fact that they've been allowed to build systems like that is appalling.
- thedougd 5d ago
  Sadly service manuals aren’t commonly sold anymore and you need a subscription to a website to access factory service manuals. It’s a shame, I use to buy the service manual when I bought the car.
itsrobreally 5d ago
You may not be aware but there are a lot of proprietary PIDs on your OBD2 bus you can't interpret without specialized software - you can get like oil pressure and temperature, but not say, shift points or anything the manufacturer doesn't think you should see. True right to repair would mean all of the PIDs get documented and there is a marketplace where I can purchase software or documentation without having to be a certified brand X mechanic.
- nvme0n1p1 5d ago
  Yes and I'm just pushing back against GP who seems to think gatekeeping that access is a good thing. And it's still way better than John Deere who (according to TFA), when the tractor detects that some wires are disconnected, wants you to pay $195 to find out which ones. I'd love to move towards a world where owners can access everything, flash the firmware in the headlamps, etc. But all I can do as an individual is vote with my wallet and avoid the 2020s computers-on-wheels.
- jonhohle 5d ago
  I’m not sticking up for car manufacturers, but at what size or capacity should you be required to document and publish these things? It requires employer time and effort and has a cost associated with it. As a counter argument: I was just looking at a small open source utility. As I was going through the code I found cases where certain arguments could be set to magic values that cause useful, but undocumented behavior. Should the developers be forced to document these options? I don’t think a manufacturer should be able to lock you out of reading diagnostics on your own devices, or that anyone should be prevented from reverse engineering what those values mean. But I also don’t think there should be any requirement that they are forced to do additional work. That seems just as immoral.
  - vlovich123 5d ago
    > I don’t think a manufacturer should be able to lock you out of reading diagnostics on your own devices, or that anyone should be prevented from reverse engineering what those values mean. But they do do that. Also what’s the difference between a lot of obfuscation and prevention and how will you enforce that without lawsuits and discovery? Also, what is those values have the ability to do damage and cause safety issues? Like losing your own software onto a control by wire car? Then you can rent a car and install your own software surreptitiously.

loopies 5d ago

What you want is the service manual. Owner manual should be implicit. OBD port can work for some cars, for some of the data. But other cars do have specialized gear they require to either access either reset some stuff in some of the car's computers.

somehnguy 5d ago
Yeah the owners and service manuals are two very very different things. You won't be performing much maintenance with the owners manual besides the absolute basics, like checking your oil. The cheap OBD2 readers lack the vast majority of data and tools you would want to use for service as well. There are aftermarket options but most manufacturers want you to subscribe to their service tools - often charged per monthly plus an additional a fee per VIN it touches. These cost in the hundreds to thousands. It can be pretty frustrating as a shadetree mechanic.
- lazide 5d ago
  Notably, some vehicles like the Toyota Highlander you can’t even figure out when you need to change the spark plugs, let alone what kind of spark plugs you need from the owners manual. Theoretically, they are to be replaced at 120k miles (!!) but they won’t even tell you that in the owners manual. Insane.
  - somehnguy 5d ago
    It is, yeah. The owners manual for my current vehicle seems to mostly contain walkthroughs about the infotainment and other tech features. The section related to maintenance is tiny in comparison. You're probably aware of this already but luckily a lot of service manuals can be found online in PDF form. Somewhat related but I was going through an older relatives belongings not too long ago to help cleanup and found a bunch of old manuals for various household things. The detail included in them was beautiful to see - full wiring diagrams, mechanical diagrams, etc.
    - skeeter2020 5d ago
      >> You're probably aware of this already but luckily a lot of service manuals can be found online in PDF form. Not official ones for John Deere tractors unless they were leaked from authorized service agents!
      - BenjiWiebe 5d ago
        And those get taken down when JD finds them.
  - sokoloff 5d ago
    The change interval is in the Warranty and Maintenance Guide, not in the main owner’s manual. (This is still part of the in-glovebox manuals, not a service-center manual.) One example: https://assets.sia.toyota.com/publications/en/omms-s/T-MMS-17Highlander/pdf/T-MMS-17Highlander.pdf https://assets.sia.toyota.com/publications/en/omms-s/T-MMS-1...
27183 5d ago
Reading codes is only part of it. For the last quarter century or so (some manufacturers more than others) if you replace certain components (radio, any computer module) you need to update the ECU to recognize the new component. This requires proprietary software and in many cases proprietary hardware as well. These "features" are marketed as an "anti-theft" mechanism. This renders some repairs basically impossible for the end user to perform. The fact that they've been allowed to build systems like that is appalling.
thedougd 5d ago
Sadly service manuals aren’t commonly sold anymore and you need a subscription to a website to access factory service manuals. It’s a shame, I use to buy the service manual when I bought the car.

itsrobreally 5d ago

You may not be aware but there are a lot of proprietary PIDs on your OBD2 bus you can't interpret without specialized software - you can get like oil pressure and temperature, but not say, shift points or anything the manufacturer doesn't think you should see. True right to repair would mean all of the PIDs get documented and there is a marketplace where I can purchase software or documentation without having to be a certified brand X mechanic.

nvme0n1p1 5d ago
Yes and I'm just pushing back against GP who seems to think gatekeeping that access is a good thing. And it's still way better than John Deere who (according to TFA), when the tractor detects that some wires are disconnected, wants you to pay $195 to find out which ones. I'd love to move towards a world where owners can access everything, flash the firmware in the headlamps, etc. But all I can do as an individual is vote with my wallet and avoid the 2020s computers-on-wheels.
jonhohle 5d ago
I’m not sticking up for car manufacturers, but at what size or capacity should you be required to document and publish these things? It requires employer time and effort and has a cost associated with it. As a counter argument: I was just looking at a small open source utility. As I was going through the code I found cases where certain arguments could be set to magic values that cause useful, but undocumented behavior. Should the developers be forced to document these options? I don’t think a manufacturer should be able to lock you out of reading diagnostics on your own devices, or that anyone should be prevented from reverse engineering what those values mean. But I also don’t think there should be any requirement that they are forced to do additional work. That seems just as immoral.
- vlovich123 5d ago
  > I don’t think a manufacturer should be able to lock you out of reading diagnostics on your own devices, or that anyone should be prevented from reverse engineering what those values mean. But they do do that. Also what’s the difference between a lot of obfuscation and prevention and how will you enforce that without lawsuits and discovery? Also, what is those values have the ability to do damage and cause safety issues? Like losing your own software onto a control by wire car? Then you can rent a car and install your own software surreptitiously.