On-Board-Diagnosis (OBD), is used to monitor and diagnose control units in vehicles.
The functions are monitored for errors, and in the event of an error, these are stored in an fault log, measurement values and setting options are made available. This enables the workshop to read out any errors that have occurred (fault codes) from the respective error memories and to check the correct function via measurement values.
An OBD system consists of at least one control unit that uses measured values from various sensors (e.g. oxygen sensors) to control actuators (e.g. injection nozzles) to achieve the desired behaviour. A modern vehicle can contain countless ECUs, each supporting hundreds of parameters that can be accessed via the DLC (Diagnostic Link Connector, obd-2-plug ) using an OBD diagnostic device.
Apps are available for mobile devices that display real-time data from the respective ECUs (virtual instrument panel). One example is the OBD app Drivedeck. For Microsoft Windows, for example, there is the OBD-2 software KOBD2Check and VCDS for manufacturer-specific OBD on Audi, Seat, Skoda and VW. An OBD diagnostic device with its own display, which is independent of basic devices such as mobile phones, PCs or laptops, is practical for diagnosis in the workshop.
The readout of errors or measured values in the respective control unit via OBD is usually done by CAN bus or K-Line , in older vehicles more rarely also by PWM (pulse width modulation) or VPW (variable pulse width). Next-generation vehicles use Ethernet (DoIP ). From 2021, models from Audi, Seat, Skoda and Volkswagen will use the mechanism SFD to regulate access to control units.
OBD-2 stands for On Board Diagnostics of the second development stage. OBD-2 is available as EOBD in the EU for the following vehicles:
- from 1.1.2000 for petrol cars
- from 1.1.2003 for Diesel and gas passenger cars
- from 1.1.2005 for trucks
- from 1.1.2017 for motorbikes
Corresponding vehicles have a obd-2-plug for connecting a diagnostic system. However, the socket itself is not an indication of the OBD-2 capability of the vehicle, because it was often also used on vehicles that only support manufacturer-specific diagnostics.
Efforts are being made to harmonise emission-related diagnostics worldwide; the corresponding standard WWH-OBD has been in development since 2014.
Various providers offer obd-help , which goes beyond the content of this wiki. OBD-Scanner and VCDS
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