Case IH F-1235-02 - ECU – Engine Control Unit (ECU): CAN C Bus off passive failure

The CAN controller has detected an excessive number of transmit or receive errors (often due to short circuits, open circuits, or faulty terminating resistors) and has transitioned to a 'passive' or 'bus off' state to prevent disrupting the rest of the network.

• MAGNUM AFS Connect
• Magnum AFS Connect tractors
• Puma series
• Steiger and Quadtrac series
• 240 Series Combines
• Austoft 9900 sugarcane harvesters

1. 1

   Use the Electronic Service Tool (EST) to check if the fault code is currently active or intermittent

2. 2

   Check the CAN C Bus wiring harness for shorts to ground, shorts to power (B+), or open circuits

3. 3

   With the battery disconnected, measure the resistance across the CAN C High and CAN C Low pins (should be approximately 60 ohms)

4. 4

   Check the ECU and CAN C bus connectors for pushed-out pins, corrosion, or moisture

5. 5

   Verify that the battery voltage is within specification and that the ECU has proper ground connections

1. 1

   Turn off the ignition and disconnect the battery.

2. 2

   Thoroughly inspect the wiring harness for the CAN C bus between the ECU and other modules.

   Repair any damaged wires, shorts, or open circuits.

3. 3

   Clean and secure all connector pins on the ECU and the CAN C bus network.

4. 4

   Evaluate the ECU's internal terminating resistor or CAN transceiver.

   If the wiring is intact but the resistance across the CAN C bus is incorrect, the ECU's internal terminating resistor or CAN transceiver may have failed.

5. 5

   Replace the ECU.

   If the ECU is determined to have an internal failure (and all external wiring/voltages are correct), the ECU must be replaced.

6. 6

   Reconnect the battery, turn on the ignition, and use the EST to clear the fault codes and verify the repair.