Case IH 19225 (DTC 931B) - ECU – Engine Control Unit (ECU): CAN C Bus off passive failure

This code indicates a critical communication breakdown on the CAN C data bus network. The "bus off passive" state means the controller has detected an excessive number of transmission or reception errors and has temporarily isolated itself from the network to prevent corrupting the rest of the system. This fault typically triggers an engine inducement (power loss or derate).

• MAXXUM T4E
• Case IH 240 Series Axial-Flow Combines (e.g., 7240, 8240, 9240)
• Case IH Magnum series
• Case IH Steiger series
• Case IH Puma series
• Case IH Maxxum series
• Case N-Series Loader Backhoes
• Case M-Series Dozers (e.g., 1150M)

1. 1

   Inspect the relevant harnesses and ECU connectors for damage, bent or dislocated pins, corroded terminals, or broken wires.

2. 2

   Verify that the ECU connectors are fully seated. Flex the involved harnesses while monitoring the diagnostic display to reveal intermittent breaks or shorts in the wiring.

3. 3

   Measure the CAN data bus voltages. A healthy CAN bus should show approximately 2.4V to 2.5V on both the yellow and green data wires.

4. 4

   Check the CAN bus terminators. The older 'active' terminators are a highly common failure point on Case IH equipment.

1. 1

   Resolve wiring issues

   If the harness flex test or visual inspection reveals a short or open circuit, repair the damaged wiring or replace the affected harness section.

2. 2

   Replace faulty terminators

   If the wiring is intact, the issue is likely a failed CAN bus terminator. Locate the active/passive terminators on the CAN C bus. If the machine is equipped with the older square 4-pin active terminators, it is highly recommended to replace them with the updated 3-pin cap style passive terminators.

3. 3

   Install adapter harness

   If upgrading from the old 4-pin terminator to the new 3-pin cap style, install the OEM adapter harness to make the connection.

4. 4

   Perform Inducement Unlock / Counter Reset

   CRITICAL STEP: Because this fault causes an engine inducement (derate), simply fixing the physical problem will not clear the code. You must use a certified diagnostic scan tool (such as the Case IH EST or Jaltest) to perform an Inducement Unlock / Counter Reset to restore full engine power.