Very basic question


Hi All,

I am new to the ODBII arena, so there’s a lot to learn for me. I have a few basic questions related to the code lookup tables, themselves:

  • Are the lookup tables in the microcontroller/reader hardware, or are those hosted in whatever app is talking to the reader?
  • My understanding is that the codes are manufacturer-specific - or at least a subset of them for a given vehicle. Is that also true?

I’m happy to do my homework on this stuff, but I figured this may be a great place for some pointers to some of the better sources out there.



The hardware just provides an interface. It translates the vehicle’s OBDII signals into data which a computer (or smartphone etc.) is able to understand. It is then up to the software to present it in a way a human can understand.

There is a set of data that the manufacturer is mandated by law to provide, and it is standardized. Things like RPM, water temperature, etc. The protocol for retrieving stored trouble codes (DTCs) is also legislated and standardized.

However, the vast majority of data on a vehicle’s bus is the manufacturer’s own secret sauce. It is possible to reverse engineer some of it though, and you’ll find some on the web. More expensive tools licensed the secret recipe under NDA and will have more features.

The wiki article is a good start.

“The Car Hacker’s handbook” on the Macchina store page is good too.