Case IH 12836 – Cab Control Module (CCM) / Vehicle Controller: Failure detection 'HighCurrent' at internal backup valve (BUV)

The controller has detected an abnormally high electrical current draw on the circuit responsible for operating the internal backup valve (BUV), which is an integral component of the tractor's trailer brake control system.

• MAXXUM T4E
• Farmall 40
• Farmall 45
• Farmall 50
• Farmall 115U Efficient Power
• Maxxum
• Puma

1. 1

   Inspect the wiring harness and connectors from the Cab Control Module to the trailer brake valve assembly for chafed insulation, pinched wires, or exposed copper shorting to ground or another wire.

2. 2

   Disconnect the connector at the internal backup valve (BUV) and measure resistance across the solenoid coil pins using a multimeter. An extremely low resistance reading indicates an internal short.

3. 3

   With the valve disconnected, turn the key on and check if the high current code changes to an 'Interruption/LowCurrent' code (12835). If it does, the wiring is likely fine and the valve is the culprit.

1. 1

   Disconnect Power

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

2. 2

   Access the Valve

   Locate the trailer brake control valve assembly (usually mounted near the rear axle or hydraulic remotes).

3. 3

   Repair Wiring

   If the diagnostic checks revealed a short in the wiring harness, repair the damaged section using weather-sealed heat shrink connectors and re-loom the harness.

4. 4

   Replace the Valve/Solenoid

   If the wiring is intact but the BUV solenoid failed the resistance test, replace the internal backup valve solenoid. Note: On many Case IH trailer brake blocks, internal solenoids are not serviced separately, requiring the replacement of the entire Trailer Brake Valve assembly.

5. 5

   Reassemble and Clear Codes

   Reconnect the electrical harness and the battery. Use the tractor's A-Pillar Hub (APH) display or a dealer diagnostic tool to clear the inactive fault codes. Test the trailer brake system to ensure the code does not return.