Case IH 639-31 - ITBV – Intelligent Trailer Brake Valve (ITBV) Electronic Control Unit (ECU): Trailer brake controller communication fault

The main vehicle controller has lost communication with the trailer brake controller, or the CAN data packets being transmitted are corrupted or timing out.

• MAGNUM AFS Connect
• Case IH AFS Connect Magnum Tractors (Models 180, 200, 220, 240, 250, 280, 310, 340, 380) with CVT or Full Power Shift transmissions (Tier 4B)

1. 1

   Check power supply to the ITBV by inspecting the fuse panel for blown fuses, specifically Fuse F-030 (Intelligent Trailer Brake Valve UNSW B+ 10A) and Fuse F-018 (ISOBUS ECU power trailer 20A).

2. 2

   Inspect the CAN communication line for an open circuit, short circuit to positive (battery), or short circuit to ground.

3. 3

   Check the CAN bus timing configuration, hardware compatibility, and network connection contacts.

4. 4

   Measure the CAN bus termination resistance to ensure the network is properly terminated (typically 60 ohms across CAN High and CAN Low with the battery disconnected).

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the battery to prevent electrical shorts during testing.

2. 2

   Locate the ITBV

   Locate the Intelligent Trailer Brake Valve and its attached ECU/wiring harness (usually mounted near the rear remote valves/air reservoirs).

3. 3

   Inspect Harness & Connectors

   Disconnect the harness from the ITBV ECU. Inspect the pins for corrosion, moisture ingress, or pushed-back pins.

4. 4

   Test CAN Lines

   Using a multimeter, test the CAN High and CAN Low wires from the ITBV connector back to the BCM for continuity. Repair any chafed or broken wires.

5. 5

   Replace the ECU

   If the wiring, fuses, and termination resistors test perfectly but the 639-31 communication fault remains active, the ITBV Electronic Control Unit has failed internally and must be replaced.

6. 6

   Reassembly and Programming

   Install the new ITBV ECU. Note that new modules may require flashing with the correct software version (e.g., software part number 51595354) using the OEM diagnostic tool.

7. 7

   Clear Codes

   Reconnect the battery, turn the key on, clear the fault codes, and test the trailer brake system for proper operation.