obd-ii

  On Board Diagnostics.

OBD-II (OnBoard Diagnostics version 2) is a common hardware diagnostics interface that is present on all cars sold in the United States after 1996. It is present in some earlier vehicles. OBD-II is mandated by CARB, the California Air Resource Board. OBD-II is primarily a read-only interface for obtaining DTCs (Diagnostic Trouble Codes). OBD-II also defines several commands, such as output state control, self test modes, and KAM (Keep Alive Memory) reset. The OBD-II connector is identical in all models, but three different protocols are commonly used to communicate. These are:

VPW (General Motors)
PWM (Ford)
ISO9141 (Chrysler, Asian, and European)

OBD-II provides information such as:

Speed
RPM
Oxygen sensor
Error codes

and more. For a list of generic OBD-II codes, see the Table of OBD-II Codes.

CAN BUS

Some newer cars (usually post 2001) also support the CAN BUS, a local area network in some cars that also gives access to additional hardware like radios, navigation systems, and more. CAN BUS devices are usually connected to via the OBD-II connector.

Interfaces

There are a number of multi-thousand dollar interfaces available to professional mechanics, but hobbyists can also connect their PCs to their cars using inexpensive adapters like the following:

Obd-ii

CAN BUS

Interfaces

See Also