Description of On-Board Diagnostics

On Board Diagnostics (OBD) functions
The following functions are possible:
On Board Diagnostic (OBD) will assist you in performing systematic troubleshooting. The VAG scan tool 1551/1552 or VAS5051 tester enable you to utilize the potentials of On Board Diagnostic (OBD). It is necessary for this purpose that the scan tool and the corresponding control module exchange information. In other words, they have to communicate with one another.
The Data Link Connector (DLC) is the interface for achievement of communication between the control module and the scan tool.
Start troubleshooting by connecting the scan tool to the Data Link Connector (DLC). Then set up communication to the control module of the relevant system.
Once communication has been established, you can select functions which provide you with the system to be checked for the purpose of troubleshooting. The functions are program routines defined within the scope of On Board Diagnostic (OBD). Their use is described in the respective topics. Firstly check the control module version and then start at Function 02, "Check DTC Memory".
The codes stored are displayed on the display of the scan tool. Via DTC tables, the troubleshooting information guides you to the possible causes and to systematic repair procedures. The DTC tables can be found in the respective topics.
On Board Diagnostic (OBD) differentiates between "static" and "sporadic" malfunctions. If a malfunction stored as a "static" malfunction is no longer present after switching-on the ignition, the malfunction is reclassified as a "sporadic" malfunction.
Sporadically occurring malfunctions are indicated as such. The code "/SP" appears on the right on the tester display.
A sporadic malfunction which does not recur over a specific number of driving cycles is automatically deleted.
Static malfunctions are stored until the DTC memory is cleared by the scan tool.
The control module version must first be checked before a control module is changed. The version appears on the display, complete with code, following setting-up of communication between the scan tool and the control module.