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Diagnostics communication

Diagnostics communication

Diagnostics communication is performed via the cable from pin 11 of the ESP control module to pin 8 of the data link connector, and from there directly to the diagnostic instrument.

The diagnostic tool communicates digitally and serially with the ESP system. With digital communication, the difference in voltage between the lead and ground has two values, in this case about 0 V and B+. The information is coded so that different combinations of 0 V and B+ pulses have different meanings.

With serial communication, the information is sent in “packets” which are sent one after the other in very quick succession.



Diagnostics

If communication with the system cannot be established, the fault could either be in the car or the diagnostic tool. If the diagnostic tool cannot establish communication with the same system in another car, then the fault is in the car.

First check that the control module is active - it should test the ABS warning lamps as soon as the ignition is switched on. If the control module is active, then the fault can probably be traced to the lead between it and the data link connector.