ABOUT OBD-II ADAPTER
On-board diagnostics [8] (OBD) is an automotive term
referring to a vehicle's self-diagnostic and reporting capability.
OBD systems give the vehicle owner or repair technician
access to the status of the various vehicle sub-systems. The
amount of diagnostic information available via OBD has
varied widely since its introduction in the early 1980s'
versions of on-board vehicle computers. Early versions of
OBD would simply illuminate a malfunction indicator light or
"idiot light" if a problem was detected but would not provide
any information as to the nature of the problem. Modern OBD
implementations use a standardized digital communications
port to provide real-time data in addition to a standardized
series of diagnostic trouble codes (DTCs) which allow one to
rapidly identify and remedy malfunctions within the vehicle.
OBD 1.5 refers to a partial implementation of OBD-II which
General Motors used on some vehicles in 1994 and 1995.
OBD-II is an improvement over OBD-I in both capability and
standardization. The OBD-II standard specifies the type of
diagnostic connector and its pin out, the electrical signaling
protocols available, and the messaging format. It also provides
a candidate list of vehicle parameters to monitor along with
how to encode the data for each. There is a pin in the
connector that provides power for the scan tool from the
vehicle battery, which eliminates the need to connect a scan
tool to a power source separately. However, some technicians
might still connect the scan tool to an auxiliary power source
to protect data in the unusual event that a vehicle experiences
a loss of electrical power due to a malfunction. Finally, the
OBD-II standard provides an extensible list of DTCs. As a result of this standardization, a single device can query the onboard computer(s) in any vehicle. This OBD-II came in two
models OBD-IIA and OBD-IIB.
The OBD-II specification provides for a standardized
hardware interface—the female 16-pin (2x8) J1962 connector
[8]. The OBD-II connector is required to be within 2 feet (0.61
m) of the steering wheel within reach of the driver.