Case IH 3096 – Engine Control Module (ECM): Tier 3: ECM Bus Off on CAN A / Tier 4a: ECM Bus Off on Vehicle CAN

The controller has detected a complete loss of communication (a Bus Off state) on the CAN A (Vehicle CAN) network. The system logs this code when interference or a disconnection on the CAN A bus is present for more than 500 milliseconds, preventing the engine controller from broadcasting or receiving messages to/from the rest of the tractor.

• skid steer
• Steiger T4B
• Farmall
• Case IH Magnum Series (235, 260, 290, 315, 340 - Series 4)
• Case IH Steiger Series
• Case IH Puma Series
• Case IH Maxxum Series
• Case IH Farmall Series

1. 1

   Verify the tractor's battery voltage is sufficient and that the ECM has clean, tight ground connections.

2. 2

   With the key off and the battery disconnected, measure the resistance across the CAN High and CAN Low pins at the diagnostic connector (should read approximately 60 ohms).

3. 3

   Visually inspect the CAN A / Vehicle CAN wiring harness between the ECM and the cab/Vehicle Control Module (VCM) for chafed wires, rodent damage, or pinched harnesses.

4. 4

   Disconnect the ECM connectors and instrument panel/cab bulkhead connectors (specifically connector X009) to check for pushed-out pins, corrosion, or moisture intrusion.

1. 1

   Power Down

   Turn off the ignition and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Isolate the Fault

   If the CAN resistance measured during diagnostics is 120 ohms, one terminating resistor or its wiring is broken. If it is 0 ohms, there is a short. Use a multimeter to trace the CAN High and CAN Low wires from the ECM to the cab bulkhead.

3. 3

   Repair Wiring

   Splice and solder any broken or chafed CAN wires. Use proper heat-shrink tubing to maintain weatherproofing. Crucial: Ensure the twisted-pair configuration of the CAN wires is maintained (typically 1 twist per inch) to prevent electromagnetic interference.

4. 4

   Clean/Replace Connectors

   If corrosion is found at the ECM or bulkhead connectors, clean the pins with electrical contact cleaner. Replace any damaged pins or connector housings.

5. 5

   Reassemble and Test

   Reconnect all harnesses and the battery.

6. 6

   Clear Codes

   Connect the CNH Electronic Service Tool (EST) or an equivalent diagnostic scanner to clear the inactive 3096 fault code.

7. 7

   Verify

   Start the tractor and monitor the CAN bus communication to ensure the Bus Off condition does not return.