CAN-Bus terminal resistance, Transmission Control Module (TCM) J217 to Engine Control Module (ECM) 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, testers and auxiliary items 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 → Motronic Engine Control Module (ECM) J220 , replacing 

Start diagnosis 

Removal 

• Remove the center dash panel - 1  - in the direction of the - arrow  -.

Fig 1: Identifying Right Upper Dashboard Panel

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• Remove the right upper dashboard panel.

Fig 2: Identifying Three Center Screws

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• Remove the three center screws - 1  -

Fig 3: Removing Right Upper Dashboard Panel

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• 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  -.

Fig 4: Identifying Transmission Control Module J217 & Retaining Nuts

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• Remove the retaining nuts - 3  - and the Transmission Control Module (TCM) J217 - 2  - in the direction of the - arrow  -.

• 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 → Motronic Engine Control Module (ECM) J220 , replacing  .

If the specified value was obtained:

Checking wiring 

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

• Install the Adapter F/VAG1598 (68 Pin) VAG1598/22
• Install the Adapter - 68 Pin VAG1598/18. Refer to 38 AUTOMATIC TRANSMISSION - GEARS, HYDRAULIC CONTROLS for 4 SPD. AUTOMATIC TRANSMISSION 01M and 38 - AUTOMATIC TRANSMISSION - GEARS, HYDRAULIC CONTROLS for 5 SPD. AUTOMATIC TRANSMISSION 09A .

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 (ECM) 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.

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: Reset/delete diagnostic data 
• 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 (ECM) 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:

1. Check the DTC memory. Refer to.
2. If necessary, erase the DTC memory.
3. If the DTC memory was erased, generate readiness code.

End of diagnosis