CAN-Bus, Checking

Terminal Resistance For CAN-Bus, Checking

Function
The Engine Control Module (ECM) communicates with all databus control modules via the CAN bus.

The control modules are connected via two data bus wires which are twisted together (CAN_High and CAN_Low), and exchange information (messages). Missing information on the data bus is recognized as an error by both the Engine Control Module (ECM) and by other CAN data bus control modules.

Trouble-free operation of the CAN data bus requires that it have a termination resistor. This central terminal resistor is located in the Engine Control Module (ECM).

Test requirement
- A DTC has been recognized by the CAN data bus On Board Diagnostic (OBD)

Special tools and equipment
- VAG 1598/31 adapter cable
- VAG 1526 multimeter or VAG 1715 multimeter
- VAG 1594 connector test kit
- Wiring diagram

Test sequence
- Switch ignition off.
- Remove battery.
- Disengage connector from Engine Control Module (ECM) and then disconnect it.
- Connect VAG 1598/31 adapter cable to Engine Control Module (ECM). Control module wiring harness is not connected.
- Check the termination resistor in the Engine Control Module (ECM):
- To do this, measure resistance between test box sockets 58 + 60: Specification: 60 to 72 Ohms

If resistance value is not in expected range:
- Replace Engine Control Module (ECM).

If resistance value is in expected range:
- Repair malfunction.