THEORY OF OPERATION - CONTINUED
ELECTRICAL SYSTEM - CONTINUED
CAT Data Link.
CAT data link is both an input and an output of engine ECM. Data link communicates with other ECMs on
machine and with service tools. Data link is bidirectional, meaning it can input and output information. Data link is
not a visible component. Data link consists of internal ECM circuits, related harness wiring, and diagnostic con-
Much information is available on CAT data link. ECM requires use of certain data that are sent back and forth on
CAT data link. Some shared information is described below:
ECM receives commands from CAT data link to change operating modes.
ECM receives commands from CAT data link to read service codes that are stored in ECM memory. Ser-
vice codes can also be cleared from memory.
ECM sends this information to CAT data link: engine speed, direction, status of operator error, and ECM
N OT E
All electronic control modules that use a CAT data link have a module identifier (MID).
CAT data link shows information to operator on gages, alert indicators, and in the display area.