Can-Bus Terminal Resistance, Transmission Control Module J217 To Engine Control Module J220, Checking
The Motronic Engine Control Module (ECM) -J220- 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) -J220-.
Special tools and workshop equipment required
- Multimeter.
- Wiring diagram.
Test requirement
- A CAN-Bus malfunction was recognized.
- The Engine Control Module (ECM) -J220- 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
Removal
-- Remove the center dash panel -1- in the direction of the -arrow-.
-- Remove the right upper dashboard panel.
-- Remove the three center screws -1-
-- Remove the right upper dashboard panel -1- in the direction of -arrow A- and -arrow B-.
-- Pull the Transmission Control Module (TCM) -J217- electrical harness electrical connector -1- retaining tab in the direction of the -arrow- and remove from the Transmission Control Module (TCM) -J217- -2-.
-- Remove the retaining nuts -3- and the Transmission Control Module (TCM) -J217- -2- in the direction of the -arrow-.
Start diagnosis
The Engine Control Module (ECM) -J220- must remain connected for the following step.
-- Using a Multimeter, check the Transmission Control Module (TCM) -J217- electrical harness connector T68 terminals 3 to 25 for resistance.
Specified value: 60 to 72 Ω (at approx. 20° 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, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
If no malfunction is found in the wiring:
-- Replace the Transmission Control Module (TCM) -J217-. Refer to TRANSMISSION CONTROL MODULE J217, REPLACING .
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) -J220-. Refer to MOTRONIC ENGINE CONTROL MODULE J220, REPLACING .
-- Using a Multimeter, check the Transmission Control Module (TCM) -J217- electrical harness connector T68 to the Engine Control Module (ECM) -J220- electrical harness connector T80 for resistance.
| Transmission Control Module (TCM) -J217- electrical harness connector terminals | Engine Control Module (ECM) -J220- electrical connector T80 terminals or test box sockets |
|---|---|
| 3 (Can_Bus Low) | 29 |
| 25 (Can_Bus High) | 41 |
Specified value: 1.5 Ω 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, loose or broken terminals.
-- If necessary, repair the faulty wiring connection.
If no malfunction is found in the wiring:
-- Erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY
-- Perform a road test to verify repair.
If the DTC does not return:
Repair complete, Generate readiness code. Refer to READINESS CODE .
-- End diagnosis.
If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:
-- Replace the Motronic Engine Control Module (ECM) -J220-. Refer to MOTRONIC ENGINE CONTROL MODULE J220, REPLACING .
-- Assembly is performed in the reverse of the removal.
Final procedures
After the repair work, the following work steps must be performed in the following sequence:
- Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
- If necessary, erase the DTC memory. DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
- If the DTC memory was erased, generate readiness code. READINESS CODE DESCRIPTION .
-- End of diagnosis.