Everything about OBD diagnostics

What are OBD diagnostics?

The on-board diagnostics system “OBD”  first saw service in the 2000s and therefore equips the majority of vehicles produced since that time. This tool allowing a more specific reading of error codes is connected to a socket called an “OBD port”, standing for  On-Board Diagnostic.

How does OBD work?

The On-board Diagnostic, thanks to the various sensors that inform the on-board computer, detects fault codes. When they are present, these fault codes are shown to the vehicle’s user by a display on the dashboard called an MIL (Malfunction Indicator Lamp).

To be able to translate these fault codes and translate them into human terms, a diagnostic pack is used: this is a digital tool on which are stored all possible fault codes for a vehicle according to its options, year of build, engine type, as well as the various technologies it uses.

How do you decrypt a fault code?

The first letter indicates the fault code family:

  • P: Powertrain, namely the engine and the gearbox
  • C: Chassis
  • B: Bodywork
  • U: Network

The first digit indicates whether the code is generic or not (green digit):

  • 0: General issue
  • 1: Manufacturer-specific issue

The three last digits correspond with:

  • 01 and 2: to check the air/fuel mix
  • 3: for the ignition system
  • 4: to check for auxiliary emissions
  • 5: to check engine idling

Source : http://www.outilsobdfacile.fr/