CAN-Bus Terminal Resistance, Transmission Control Module (TCM) J217 to Engine Control Module (ECM) J623 , Checking

CAN-Bus Terminal Resistance, Transmission Control Module (TCM) J217 To Engine Control Module (ECM) J623, Checking

The Engine Control Module (ECM) J623 communicates with all databus 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.

Procedure







- Disconnect the Transmission Control Module (TCM) J217 electrical harness connector - direction of the arrow -.

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

- Using a Multimeter, check the Transmission Control Module (TCM) J217 electrical harness connector terminals 2 to 6 for resistance.
Specified value: 60 to 72 Ohms (at approx. 20 degrees C)

If the specified value was not obtained:
- Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).
- Check the wiring connection for damage, corrosion, lose or broken terminals.
- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring:
- Replace the Engine Control Module (ECM) J623.

If the specified value was obtained:

Checking wiring
If the manufacturers test box is being used. Perform the following step.

- Install the test box.

If the manufacturers test box is not being used. Perform the following step.
- Remove the Engine Control Module (ECM) J623.
- Using a Multimeter, check the Transmission Control Module (TCM) J217 electrical harness connector to the Engine Control Module (ECM) J623 electrical harness connector T94 for resistance.

Transmission Control Module Engine Control Module
(TCM) J217 electrical harness (ECM) J623 electrical connector
connector terminals T94 terminals or test box sockets
2 (Can_Bus Low) 67
6 (Can_Bus High) 68

Specified value: 1.5 Ohms Max.

If the specified value was not obtained:
- Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).
- Check the wiring connection for damage, corrosion, lose or broken terminals.
- If necessary, repair the faulty wiring connection.

If no malfunction is found in the wiring:
- Replace the Mechatronic unit in the transmission.

Final procedures
After the repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory.
2. If necessary, erase the DTC memory.
3. If the DTC memory was erased, generate readiness code.

- End of diagnosis.