Thread: Relationship between ODB and CanBus

not sure if this is right in ralation to your cars ECU but generally CAN = Controler Area Network same as LAN = Local Area Network its just a means of transmiting data round the car.
OBD = On Board Diagnostics, its the software that works out if everything is within parameters and if not tries to correct it or warn you there is a problem.
This isnt a very good analagy but its like windows uses the LAN to talk to servers, printers and stuff where obd/obdII uses CAN to talk to other bits of the car like the steering which usually has its own ecu if its electric.

http://www.freescale.com/webapp/sps/...02WcbfNZnLNnms has stuff on CAN if your interested.

That make sense to you?

Originally Posted by Cruizer

I know that ODBII has three protocals ISO, VPW and PWM. I think ODB is the interface into the cars ecu, allowing you to see sensor outputs from the car as well as error codes etc.

The newest revision of the OBD2 spec (SAE J1979) also permits CAN for diagnostics. Older documents only mentioned the other three protocols.

Originally Posted by Cruizer

I am told that using CanBus I can interface with my steering wheel controls so it will pickup on the press of the steering wheel controls is this correct? So is canbus an extension of ODB that interfaces with the rest of the car.

CAN is just another vehicle networking protocol. It's much faster than the other three protocols that you mentioned, and it's common on newer vehicles.

Sure, you can sometimes interface with the steering wheel controls. My car uses PWM for the stock audio equipment. Others use CAN. But no matter what protocol they use, you still need to know (or reverse engineer) the messages and commands. That's the difficult part!

Thanks for the response guys.

ElmScans all in one list ISO15765-4 (CAN) as a supported protocol. Does that mean that CAN is actually a variation of ISO?

The way that I understand it is that CAN is just a network name and relates to the highest level of data transfer in the car. Most CAN cars also have LIN networks and mine has the lovely MOST network for all infotainment controlling (anyone know how to access, edit, or otherwise view that one?? im desperate for help!).

CAN handles the time critical stuff like safety features, engine workings, all those things that make you go, stop, and protect you from injury. The LIN is a secondary layer that transport functions like "A/C up" or "cruise control on" or "heat seater on" type stuff that isnt vital to the operation of the car and its main functions and moves much slower (still really really fast to you and me though). But a signal is sent out over the network and picked up by certain computers to achieve the desired result of a button push or hard brake. Its just a matter of which button goes to which network as they are layerd.

CAN is a certain variation of ISO standards and all cars imported or built in the US have to have this as their standard for MY08+. So those of us whith CAN now will hopefully see an increase in available software and hardware options to tune, reprogram, upgrade, or otherwise edit the computer components in one's vehicle. Okay, ill stop now and im very tired and probably making no sense and just confusing you more, haha. Hope I helped somewhat