Basic information on self-diagnosis of pneumatic suspension system, two-wheel and four-wheel systems — AUDI

Self-diagnosis-capable systems are characterized by a control unit which detects faults during operation of the vehicle and stores them in a fault memory, the information contained in which remains stored even in case of absence of battery voltage.

Self-diagnosis relates to the electrical and electronic part of a system, i.e., only faults which influence electrical signals are detected.

Self-diagnosis will assist you in performing systematic fault-detection. The V.A.G Fault Reader 1551/1552 or VAS 5051 tester enable you to utilize the potentials of self-diagnosis. It is necessary for this purpose that the fault reader and the corresponding control unit exchange information. In other words, they have to communicate with one another.

The diagnostic connector is the interface for achievement of communication between the control unit and the fault reader.

Start fault-detection by connecting the fault reader to the diagnostic connector. Then set up communication to the control unit of the relevant system.
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Once communication has been established, you can select functions which provide you with the system to be checked for the purpose of fault-detection. The functions are program routines defined within the scope of self-diagnosis. Their use is described in the respective topic sections of this workshop manual. Firstly check the control-unit version and then start at Function 02, "Poll fault memory" =>Page
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The faults stored are displayed on the display of the fault reader. Via fault tables, the fault-finding information guides you to the possible causes and to systematic repair procedures. The fault tables can be found in the respective topic sections of this workshop manual.

Self-diagnosis differentiates between "static" and "sporadic" faults. If a fault stored as a "static" fault is no longer present after switching-on the ignition, the fault is reclassified as a "sporadic" fault.

Sporadically occurring faults are indicated as such. The code "/SP" appears on the right on the tester display.

A sporadic fault which does not recur over a specific number of driving cycles is automatically deleted.

Static faults are stored until the fault memory is cleared by the fault reader.

The control-unit version must first be polled before a control unit is changed. The version appears on the display, complete with code, following setting-up of communication between the fault reader and the control unit.