On-board diagnostics (OBD) is an automotive term referring to a vehicle's self-diagnostic and reporting system. OBD
systems give the vehicle owner or repair technician access to the status of the various vehicle emissions and control systems.
The products are under continuous development. Vehicles and components produced after the
above date may therefore have different specifications and repair methods. When this is deemed to
have a significant bearing on this manual, an updated version of this manual will be issued to cover
What does the OBD system do?
OBD code is stored in the OBD system and can only be accessed by connecting a scan, or diagnostic tool into the EOBD diagnostic socket and reading the DTC off the display of the scanner.
OBD-2 Engine trouble codes are divided 4 different systems according to their first letter.
covers functions that are shared among computers and systems on the vehicle.
OBD2 Code Structure
First unit identifies the type of obd error code:
Pxxxx for powertrain
Bxxxx for body
Cxxxx for chassis
Uxxxx for class 2 network
Second digit shows whether the code is manufacturer unique or not:
x0xxx for government-required code
x1xxx for manufacturer-specific code
Third digit shows us what system the trouble code references:
xx1xx/xx2xx show air and fuel measurements
xx3xx shows ignition system
xx4xx shows emissions systems
xx5xx references speed/idle control
xx6xx deals with computer systems
xx7xx/xx8xx involve the transmission
xx9xx notates input/output signals and controls
Digits four and five show the specific failure code.
xxx00 to xxx99 - these are based on the systems defined in the third digit.