OBD (on-board diagnosis) means that
- Emission-related components and systems are monitored by the vehicle whilst driving
- Any malfunctions are recorded and indicated by a warning lamp (MIL)
- This information can be read by a diagnostic tester
A further purpose of OBD is to protect vulnerable components such as catalytic converters.
In these operating instructions, OBD is always used to refer to the standard OBD-2 (OBD II). OBD-2 has been obligatory in the USA for all new vehicles since 1st January 1996. In the EU, OBD-2 was introduced for new vehicles with gasoline engine in January 2001 with the EURO-3 standard and for diesel vehicles in January 2004. EOBD is the abbreviation for European on-board diagnosis based on OBD-2.
The OBD diagnostic system is integrated into the electronic control unit and constantly monitors defined emission-related components in the vehicle. The malfunction indicator light (MIL) informs the driver of OBD faults reported by the electronic control unit.
A minimum of five monitoring systems are provided:
- Emission-related components
- Missing combustion
- Fuel system
- Upstream and downstream Lambda sensors
- Catalytic converter efficiency
- Exhaust gas recirculation
- Secondary air system
The following are permanently monitored:
- Missing combustion
- Fuel system (injection times)
- Circuits for emission-related components
The following are monitored once per drive cycle:
- Lambda sensor function
- Catalytic converter function
Speed, temperature and Lambda sensor values can also be read out by way of the OBD diagnostic socket.