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

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2001 Volkswagen Jetta, 2001 Volkswagen Golf, 2000 Volkswagen Jetta, 2000 Volkswagen Golf, and 1999 Volkswagen Jetta. However, it is still accessible from the selected car via links, so may be relevant.

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

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.

Fig 1: CAN-Bus Circuit Diagram

Courtesy of VOLKSWAGEN UNITED STATES, INC.

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.

Special tools, testers and auxiliary items required

Test box V.A.G 1598/22 (through my 1999)
Test box V.A.G 1598/31 (from my 2000)
Digital multimeter US 1119 (Fluke 83 or equivalent)
Adapter set V.A.G 1594

Wiring diagram

Vehicles with manual transmission

Test box V.A.G 1598/21

Vehicles with automatic transmission

Test box V.A.G 1598/18