Public data line is used for connection to F3-D truck scanner, Data line is used for communication with ECU as well as information communication with other vehicle electronic devices, such as electronic instrument panel and other devices. Some engines have two public data lines: one is in the whole wiring harness (engine side data line); another is separated from ECU harness, normally locate in cab.
Pic.4-33 shows the data lines of early electronically controlled engine. They all have a rectangular 12-pin connector. There are 3 kinds of special harness that used for different type of diagnostic data connector, when troubleshooting, maintenance technician connect appropriate diagnostic plug to diagnostic data connector, and then can download fault code saved in ECU memory. New type of electronically controlled engines all adopt standard SAE data line as shown in Pic.4-34（b）.The connection of 6-pin connector is as below, when detect communication failure between pin and truck diagnostic tool, you can measure voltage of this pin with digimer.
（a）. Used for connection with engine, vehicle diagnostic socket and Fcar F3-D truck diagnostic tool,
6-pin socket and 9-pin socket.
（b）.Standard SAE 6-pin German-made connector
A——data line（十）;voltage normally between 2.5～5V.
B——data line（—）;voltage normally between 0～2.5V.
C——Battery（12V or 24V）;12V Electric System are different from 24V Electric System, normally between 10～27V.
D——open circuit；voltage normally between 4～5V
E——Cylinder body ground；0V
F3-D heavy truck diagnostic scanner can diagnose all kinds of diesel control systems quickly and easily, especially available for China, Europe, America, Japan and Korea and so on,build-in high/low speed CAN-Bus to satisfy all Can-Bus vehicles;
Coverage: MAN, Mitsubishi Fuso, Scania, ISUZU, MACK, HINO, VOLOV, DAF, Astra, Detroit, BENZ, NISSAN UD, Catepillar, Renault,…and most of CHINA Heavy duty trucks , BUS………
Bosch, Cummins, Catepillar, Denso, Siemens, Motorola, Zexel, VITO, NanYue, Delphi, Wabco……