CAN-Bus Terminal Resistance Instrument Cluster to Data Diagnostic Connector, Checking

CAN-Bus Terminal Resistance Instrument Cluster to Data Diagnostic Connector, Checking

The Engine Control Module (ECM) (J623) communicates with all data-bus capable control modules via a CAN databus.

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 databus is recognized as a malfunction and stored.

Trouble-free operation of the CAN-bus requires that it have a terminal resistance. The central terminal resistor is located in the Engine Control Module (ECM) (J623).

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirement

• A CAN-Bus malfunction was recognized.

• The Engine Control Module (ECM) (J623) fuses OK.

• Battery voltage at least 12.5 V.

• Ignition switched off.

Test Procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check

- Disconnect the Instrument Cluster Control Module (J285) electrical harness connector T32 from the Instrument Cluster Control Module.

• The Engine Control Module (ECM) (J623) must remain connected for the following step.

- Disconnect the Data Bus On Board Diagnostic Interface (J533) electrical harness connector T32b from the diagnostic interface.

- Using a Multimeter , check continuity between J285 and J533.

Specified value: max. 1.5ohms (at approx. 20° C)






If the specified value was Not obtained:

- Check the wiring connection for an open circuit, short circuit to Battery voltage or Ground (GND).

- Check the wiring connection for damage, corrosion, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If the specified value was obtained:

- Replace the Engine Control Module (ECM) (J623). Refer to Repair Manual.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Programming and Relearning.