Component Tests and General Diagnostics

Terminal resistance for CAN-Bus, checking

Function
The Engine Control Module (ECM) communicates with all databus-capable control modules via a CAN-Bus.

These databus-capable 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 a malfunction and stored.

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).

Recommended special tools and equipment
- VAG1526 multimeter or VAG1715 multimeter
- VAG1594 connector test kit
- Wiring diagram

Test requirements
- DTC "P0600 Serial Communication Link" was detected by the Engine Control Module (ECM), Diagnostic mode 3: Check DTC memory. Diagnostic Mode 3: Check DTC Memory
- Ignition switched off.

Test sequence
- Connect test box to Engine Control Module (ECM), connect test box for wiring test. During this, wiring harness to Engine Control Module (ECM) is not connected.
- Check the central termination resistor in the Engine Control Module (ECM):
- To do this, measure resistance between test box socket 58 + 60:
Specified value: 60...72 ohms

If resistance value is not in expected range:

- Replace Motronic Engine Control Module (ECM) -J220-.

If resistance value is in expected range:
- Disconnect test box from Engine Control Module (ECM).
- Connect test box to control module wiring harness.
- Check CAN data bus wires for short circuit to each other:
- To do this, perform a resistance measurement between test box sockets 58 + 60:
Specified value: Infinite Ohms

If specified value is obtained (wires have no shorts):
- Eliminate error in wires (see wiring diagram).