2.General Information
2.1 On-Board Diagnostics(OBD)II
The first generation of On-Board Diagnostics (called OBD I) was
developedby the California Air Resources Board (CARB )and
implemented in 1988 tomonitor some of the emission control
components on vehicles.As technologyevolved and the desire to
improve the On-Board Diagnostic system increased,a new generation
of On-Board Diagnostic system was developed,This second generation
of On-Board Diagnostic regulations is called "OBD II".
The OBD II system is designed to monitor emission control systems
and key engine components by performing either continuous or
periodic tests of specific omponents and vehicle conditions.When a
problem is detected,the OBD II system turns on a warning lamp(MIL)
on the vehicle instrument panel to alert the driver typically with the
phrase"Check Engine" or "Service Engine Soon".
The system will also store important information about the detected
malfunction so the a technician can accurately find and fix the
problem,The system will give the following information:
1) Whether the Malfuncaion Indicator Lght (MIL) is commanded 'on'
or 'off';
2) Which,if any ,Diagnostic Trouble Codes (DTCs)are sored;
3) Readiness Monitor status.
2.2 Diagnostic Trouble Codes(DTCs)
OBD II Diagnostic Trouble Codes are codes that are stored by the
on-board computer diagnostic system in response to a problem found
in vehicle.These codes identify a particular problem area and are
intendedd to provide you with a guide as to where a fault might be
occurring within a vehicle.OBD II Diagnostic Trouble Codes consist
of a five-digit alphanumeric code:The first character, a letter,identifies
which control system sets the code.The other four characters,all
numbers ,provide additional information on where the DTC originated
and the operating conditions that caused it to occur,Below is an example
to illustrate the structure of the digits:
2