On�board Diagnostics (OBD)
The main reason for introducing the OBD is "Guideline 98/69/EC for reducing motor vehicle emissions" dated 28.12.1998.
A further reason for introducing OBD is that, owing to increasing service intervals and increasing intervals between the exhaust gas emissions tests, malfunctions may, in some instances, not be detected in due time.
In order to fulfil future statutory requirements with regard to environmental protection, higher demands are placed on individual components
With the introduction of diagnostic control units, the move towards on�board diagnostics has been completed.
The regulations for OBD stipulate the types and forms of electronic functions for monitoring the exhaust gas characteristics of motor vehicles.
The principle of the on�board diagnostics is to detect, store and display faults via a telltale in the instrument panel (MIL - malfunction indicator light = exhaust gas telltale). Faults can be read out via a diagnostic unit. Parts in the vehicle relating to exhaust gas emissions can thus be monitored constantly.
The following components are monitored:
- Catalytic converter(s)
- Crankshaft sensor
- Camshaft sensor
- Throttle valve module
- Ignition module
- Mass air flow meter
- Intake air temperature sensor
- Coolant temperature sensor
- Permanent memory
- Injectors
10.2.9 On�board Diagnostics (OBD)
If malfunctions occur in the engine management system, these may have an adverse effect on the emissions, without the driver being aware of this fault. Misfiring is one such fault which can lead to destruction of the catalytic converter.
Considerably more information can be read from the fault memory using the OBD additional monitoring functions and additional information in comparison to the previous methods used.
With OBD, all systems and processes affecting exhaust gas emissions are monitored, not only purely electrical components.
The following systems, components and processes are monitored:
- Oxygen sensors
- Misfiring
- Exhaust gas recirculation system
- Tank vent system
- Fuel system
- Components and assemblies relating to emissions
- Control units
If deviations from the specified tolerances are determined, an appropriate trouble code is stored in the permanent memory. If a fault relating to exhaust emissions reoccurs, the exhaust gas telltale is activated.