Case IH 17692 (F-1235-31) - ECU – Engine Control Module (ECM) / Vehicle Controller: Engine sensor CAN bus - bus off passive failure

The Controller Area Network (CAN) bus dedicated to communicating with the engine sensors has experienced a critical communication failure. When a module detects too many transmission or reception errors on the CAN network, it enters a "bus off" passive state. This is a self-preservation mechanism where the node stops transmitting data to prevent corrupting or crashing the rest of the vehicle's communication network.

• VESTRUM CVX
• Farmall 40
• Farmall 45
• Farmall 50
• Farmall 115U Efficient Power
• 240 Series Axial-Flow Combines

1. 1

   Verify the supply voltage to the ECU and engine sensors to ensure it is within the required range.

2. 2

   Inspect the engine sensor CAN wiring for physical damage, looking for open circuits, short circuits to ground, or short circuits to battery voltage.

3. 3

   With the battery disconnected, measure the resistance between the CAN High and CAN Low pins on the diagnostic connector or sensor harness (should read approximately 60 ohms, indicating two 120-ohm terminating resistors in parallel).

4. 4

   Disconnect the engine sensors on that specific bus one by one to isolate if a faulty sensor (hardware or firmware) is pulling the entire CAN bus down.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery terminal to prevent electrical spikes during testing.

2. 2

   Visual Inspection

   Locate the engine sensor CAN bus harness. Carefully inspect all connectors for water ingress, bent pins, or corrosion. Clean any affected connectors with contact cleaner.

3. 3

   Repair Wiring

   If the multimeter tests reveal a short or open circuit in the CAN lines, trace the harness to find the chafed or broken wire. Repair the wire using OEM-approved splicing methods (solder and heat shrink) or replace the affected harness section.

4. 4

   Replace Faulty Node

   If isolating the sensors revealed that a specific component (e.g., DEF quality sensor, NOx sensor, or pressure sensor) was crashing the bus, replace that specific sensor.

5. 5

   Reassemble and Power Up

   Reconnect all sensors and the battery.

6. 6

   Clear Codes and Reset Inducement

   Connect the Case IH Electronic Service Tool (EST). Clear the fault codes. Note: Because a CAN bus failure on the engine network often triggers an engine protection inducement (power derate or idle lock), you may need to perform an "Inducement Unlock / Counter Reset" via the service tool once the physical repair is complete.