CAN-Bus Terminal Resistance, Checking

CAN-Bus Terminal Resistance, Checking

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 resistance is located in the Engine Control Module (ECM).

Recommended Special Tools, Workshop Equipment, Testers, Measuring Instruments and Auxiliary Items
- V.A.G 1526 portable multimeter or V.A.G 1715 multimeter
- Adapter set V.A.G 1594
- Wiring diagram

Test Conditions
- DTC "P0600 Serial Communication Link" was detected by the Engine Control Module (ECM). Diagnostic Mode 03 - Read DTC Memory
- Ignition switched off.

Test Sequence
- Connect test box to Engine Control Module (ECM). Test Box, Connecting For Wiring Test The control module wiring harness is not connected.
- Check the central terminal resistance in the Engine Control Module (ECM):
- To do this, measure resistance between test box
socket 58 + 60:

Specified value: 60 to 72 Ohms

If Resistance Value Is not in Specified Range:
- Replace Motronic Engine Control Module (ECM) -J220-.

If Resistance Value Is in Specified Range:
- Disconnect test box from Engine Control Module (ECM).
- Connect test box to control module wiring harness.
- Check CAN-Bus wires for short circuit to each other:
- To do this, perform a resistance measurement between test box sockets 58 + 60:

Specified value: Infinity Ohms

If specified value is not obtained (wires have no short circuit to each other):
- Eliminate malfunction in CAN-Bus wires or in other CAN-Bus components according to wiring diagram.