Case IH 2291 (520330.02) - DEC – DEC: CAN 2 - Bus Off

A 'Bus Off' state occurs when a Controller Area Network (CAN) node detects too many transmission or reception errors (specifically, when its internal transmit error counter exceeds 255). To prevent corrupted data from disrupting the rest of the machine's network, the controller disables its output drivers and completely disconnects itself from the bus. This is almost always caused by a physical layer error on the CAN 2 network, such as a short circuit, an open circuit, a missing termination resistor, or a failed CAN transceiver inside a module.

• MAXXUM T4E
• VESTRUM CVX
• AFS Connect Magnum
• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Magnum 380
• Steiger
• Puma
• Maxxum

1. 1

   Check CAN 2 Resistance: With the machine powered off and the battery disconnected, measure the resistance between the CAN 2 High and CAN 2 Low pins at the diagnostic connector or DEC harness (should read approximately 60 Ohms).

2. 2

   Check for Shorts: Test for continuity between CAN 2 High and Ground, CAN 2 Low and Ground, and between CAN 2 High and CAN 2 Low. Any continuity to ground indicates a shorted wiring harness.

3. 3

   Inspect the DEC Connectors: Check the wiring harness and connectors plugging into the Driveline Electronic Control module for pushed pins, corrosion, or moisture.

4. 4

   Isolate Modules: Disconnect other modules on the CAN 2 bus one by one to see if the bus resistance normalizes or if communication is restored, as any module can pull the voltage down.

1. 1

   Power Down

   Turn off the machine and disconnect the battery to prevent electrical spikes.

2. 2

   Locate the Fault

   Based on the diagnostic checks, trace the CAN 2 wiring harness from the DEC module along the driveline/chassis. Look for areas where the harness may have rubbed against the chassis or transmission housing, causing a short.

3. 3

   Repair Wiring / Resistors

   If a broken wire or short is found, repair the wiring harness using OEM-approved splicing methods. If the bus resistance was 120 Ohms (instead of 60), locate and replace the missing or failed 120-Ohm CAN termination resistor.

4. 4

   Module Replacement (If Necessary)

   If the wiring harness and termination resistors test perfectly, the CAN transceiver inside the DEC module has likely failed. Remove the DEC module and install a replacement.

5. 5

   Clear and Test

   Reconnect the battery, turn the key to the ON position, and use the Case IH Electronic Service Tool (EST) to clear the 2291 (520330.02) fault code. Verify that the DEC module successfully communicates on CAN 2 without returning to a 'Bus Off' state.