Case IH 12805 – Trailer Brake Controller (iTBV) / MTA CCM: Plausibility check: Pressure Controller - Actual Pressure too high (on control line)

This code indicates a plausibility error where the actual hydraulic or pneumatic pressure measured on the trailer brake control line exceeds the expected or demanded pressure threshold. The system detects that the pressure controller is outputting or reading a pressure that is too high for the current brake pedal position or operating state.

• MAXXUM T4E
• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Magnum 380
• Puma 115 through 225
• Maxxum MXU100
• Maxxum MXM155
• Maxxum MXM175
• Farmall 40
• Farmall 45
• Farmall 50
• Farmall 115U

1. 1

   Pressure Peak Test: Apply the brake pedals for 10 seconds and monitor the hydraulic pump. Check if excess pressure peaks are observed, which could indicate a faulty hydraulic pump rather than a failed valve.

2. 2

   Visual Leak Inspection: Inspect the trailer brake auxiliary valve and the entire hydraulic/pneumatic braking circuit for oil or air leaks.

3. 3

   Sensor & Wiring Verification: Check the TCV (Trailer Control Valve) pressure sensor supply for a 'Short to Power' or 'Short to Ground' (which would typically trigger related codes 12803 or 12804).

4. 4

   Software/Configuration Check: Verify that the iTBV CAN communication is active and that the End-of-Line (EOL) configuration matches the vehicle setup, as incorrect datasets can cause plausibility faults.

1. 1

   Relieve System Pressure

   Safely depressurize the tractor's hydraulic and pneumatic braking systems before opening any lines.

2. 2

   Address Pump/Leak Issues

   If the diagnostic tests revealed hydraulic pump pressure spikes or auxiliary valve leaks, repair the leaks or test/replace the pump accordingly.

3. 3

   Replace the Trailer Brake Valve (iTBV)

   If the pressure regulating valve is confirmed faulty (internal failure causing high actual pressure on the control line), the iTBV assembly must be replaced. Disconnect the electrical harness from the iTBV solenoid, disconnect the air/hydraulic hoses, unbolt the valve assembly from the chassis/bracket, and install the new trailer brake valve and reconnect all lines and harnesses.

4. 4

   Bleed the System

   Bleed the tractor and trailer braking hydraulic circuits to remove any trapped air.

5. 5

   Calibrate the Controller

   If a new controller/valve is installed, the transmission clutches and braking stack must be recalibrated via the tractor's diagnostic interface to clear the plausibility mismatch.