CAN-Bus, checking (through MY 1999): Function

The Engine Control Module (ECM) (item 1) communicates with the ABS Control Module (item 2) and the Transmission Control Module (TCM) (item 3) via a CAN - Bus (item 4).

Fig 1: Can-Bus Schematic

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

At least two Control Modules capable of CAN - Bus are connected together via two CAN -Bus wires which are twisted together (CAN_High and CAN_Low) and they exchange information (messages). Missing information on the CAN-Bus will be recognized as a DTC by the Engine Control Module (ECM) as well as by other CAN-Bus Control Modules.

Two Control Modules have terminal resistors each of 120 Ω, these resistors make sure that the CAN-Bus can function without a malfunction. These terminal resistors are located in the engine and ABS Control Modules.