Case IH 12801 – Trailer Brake Control Module (iTBV) or Cab Control Module (CCM): Plausibility check: Brake Pedal - Output Invalid (brake switch high, demand pressure sensor low)

A plausibility (logic) error where the control module detects conflicting inputs. The system sees that the brake pedal switch is active or 'high' (indicating the operator is pressing the brake pedal), but the brake demand pressure sensor is reading 'low' (indicating no hydraulic or pneumatic braking pressure is actually being generated in the circuit).

• MAXXUM T4E
• Puma
• Maxxum
• Optum
• Magnum

1. 1

   Inspect the brake pedal switch to see if it is fully returning to its resting position, physically stuck closed, or if there is a short to power in the switch wiring causing it to read high constantly.

2. 2

   Test the brake demand pressure sensor output using a diagnostic tool or multimeter to verify if it reads correctly at rest and if the pressure value increases when the pedal is depressed.

3. 3

   Verify actual brake pressure by manually checking the hydraulic or pneumatic pressure in the trailer brake circuit with a mechanical gauge. If no pressure is generated when the pedal is pressed, the mechanical brake valve or master cylinder is at fault.

4. 4

   Inspect the wiring harnesses connecting the brake switch, the pressure sensor, and the ECU for chafing, corrosion, or broken wires.

1. 1

   Disconnect battery

   Disconnect the tractor's battery before beginning electrical repairs.

2. 2

   Replace brake switch

   If the brake switch is faulty: Locate the brake pedal switch at the base of the brake pedal linkage. Disconnect the wiring harness, unthread/unbolt the faulty switch, and install the replacement. Adjust the new switch so that it only activates when the pedal is actually depressed, then tighten the locknut.

3. 3

   Replace pressure sensor

   If the pressure sensor is faulty: Locate the brake demand pressure sensor on the trailer brake valve block or air/hydraulic line. Relieve any residual pressure in the system. Remove the faulty sensor, install the new sensor (ensuring any O-rings or sealing washers are in place), and reconnect the wiring harness.

4. 4

   Bleed or rebuild brake system

   If there is a mechanical pressure failure: Bleed the brake system to remove any trapped air. If pressure still cannot be generated, rebuild or replace the brake master cylinder or trailer brake valve block.

5. 5

   Finalize repair

   Reconnect the battery, clear the fault codes using a diagnostic tool, and perform a test drive to ensure the plausibility error does not return.