Diagnostics communication: Notes
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.