With Generic Scan Tool

Terminal resistance for CAN-Bus, checking

Vehicles with engine code ATQ (121-pin Engine Control Module -ECM-)

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

These CAN-Bus-capable control modules are connected via two CAN-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
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 Connector test set
- Wiring diagram

Test requirements
- DTC "P0600 Serial Communication Link" was detected by the Engine Control Module (ECM), Diagnostic mode 3: Check DTC memory. Refer to "Scan Tool Testing/Diagnostic Mode 3: Check DTC Memory"
Diagnostic Mode 3: Check DTC Memory

- Ignition switched off.

Test sequence
- Connect test box to control module wiring harness, connect test box for wiring test. Refer to "Scan Tool Connecting/Test Box, Connecting For Wiring Test".
Test Box, Connecting For Wiring Test

- 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 to 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-Bus wires for shorts among one another:
- To do this, perform a resistance measurement between test box sockets 58 + 60:
Specified value: Infinity Ohms

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