Terminal Resistance For CAN-Bus, Checking

Terminal Resistance For Can-Bus, Checking

Function
The Engine Control Module (ECM) communicates with other CAN-bus capable control modules.

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 CAN-bus is recognized as malfunction by both the Engine Control Module (ECM) and other control modules connected to the CAN-bus.

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

Test requirement
- A CAN-bus malfunction was recognized via On Board Diagnostic (OBD)

Special tools and equipment
- VAG1598/31 test box
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram

Test sequence
- Switch ignition off.
- Disengage connector from Engine Control Module (ECM) and then disconnect it.
- Connect VAG1598/31 test box to Engine Control Module (ECM). Control module wiring harness is not connected.
- Check the central termination resistor in the Engine Control Module (ECM):
- Measure resistance between test box sockets 58 and 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: