New Holland ENG 3097 – Engine Control Module (ECM) / EDC: ECM Bus Off on Engine private CAN

The engine's control module has detected a critical number of communication errors on its private Controller Area Network (CAN) bus. To prevent corrupting the rest of the network with faulty data, the module forces itself into a "Bus Off" state, effectively dropping communication on that specific line.

• T8.xxx Series
• T7 Series
• T7.220
• T7.235
• T7.250
• CR9090
• CX8080 Elevation
• CX8090 Elevation Tier 4A
• W130B
• W190B
• Magnum 235-340 (Series 4)

1. 1

   Inspect the engine wiring harness connectors at the EDC and any connected smart actuators (like the dosing module or NOx sensors) for corrosion, moisture, or pushed pins.

2. 2

   With the machine off and the battery disconnected, measure the resistance between the CAN High and CAN Low pins on the private CAN bus. A healthy CAN bus should measure approximately 60 ohms (due to two 120-ohm terminating resistors in parallel). If it reads ~120 ohms, one terminating resistor or its wiring is open. If it reads near 0 ohms, the CAN High and CAN Low wires are shorted together.

3. 3

   Check the engine private CAN wiring harness for shorts to ground, shorts to battery voltage, or open circuits.

4. 4

   Verify that the EDC is receiving proper unswitched battery voltage and has clean, tight ground connections, as voltage drops can cause CAN modules to drop offline.

1. 1

   Disconnect Power

   Turn off the main battery disconnect switch to ensure the system is safe to probe and to prevent accidental shorts.

2. 2

   Isolate the Fault

   Based on the resistance and continuity tests, isolate whether the fault lies in the main engine wiring harness, a terminating resistor, or a peripheral module on the private CAN.

3. 3

   Repair/Replace Wiring

   If a short or open circuit is found in the harness, repair the damaged wires or replace the affected engine wire harness section.

4. 4

   Replace Terminating Resistor

   If the CAN bus resistance is incorrect and a resistor is found to be open/failed, replace the CAN terminating resistor.

5. 5

   EDC Replacement (Worst Case)

   If the wiring harness, resistors, and peripheral modules all test perfectly, the internal CAN transceiver inside the EDC may have failed (as noted in a W130B loader case study). The EDC will need to be replaced and reprogrammed.

6. 6

   Clear Codes

   Reconnect the battery, turn the key on, and use a diagnostic tool (such as the CNH EST or Jaltest) to clear the fault codes and verify that the private CAN bus is communicating normally.