Case IH 12652 – Vehicle Control Module (VCM) or Trailer Brake Control Module / ABS Module: Pneumatic input - control port pressure sensor electrical fault

This fault code indicates an electrical failure (such as an open circuit, short to ground, or short to power) in the circuit for the pneumatic trailer brake control port pressure sensor. The sensor monitors the air pressure being supplied to the trailer brakes, and the electrical error means the controller is no longer receiving a valid, plausible voltage signal from this sensor.

• Puma 140
• Puma 150
• Puma 165
• Puma 185
• Puma 200
• Puma 220
• Puma 240
• Puma CVT
• Maxxum
• Vestrum 100
• Vestrum 110
• Vestrum 120
• Vestrum 130

1. 1

   Locate the pneumatic trailer brake pressure sensor on the trailer brake control valve/manifold and inspect the electrical connector for corrosion, moisture ingress, or backed-out pins.

2. 2

   Inspect the wiring harness leading to the sensor for chafing, breaks, or melted insulation.

3. 3

   Using a multimeter, verify that the sensor is receiving the correct 5V reference and ground from the ECU, and check the signal wire for continuity back to the control module.

4. 4

   Ensure there are no severe air leaks at the control port that might be causing erratic sensor readings.

1. 1

   Depressurize the System

   Turn off the tractor engine, apply the parking brake, and safely bleed all compressed air from the tractor's pneumatic trailer brake reservoirs to prevent injury.

2. 2

   Disconnect the Sensor

   Unplug the electrical harness connector from the pneumatic trailer brake pressure sensor.

3. 3

   Remove the Sensor

   Using an appropriate wrench, carefully unscrew the faulty pressure sensor from the trailer brake control valve manifold.

4. 4

   Install the New Sensor

   Thread the new sensor into the port. Ensure any required sealing washers or O-rings are in place to prevent air leaks. Torque to the manufacturer's specification.

5. 5

   Reconnect

   Plug the electrical harness back into the new sensor.

6. 6

   Test the System

   Start the tractor and allow the air compressor to build system pressure. Spray a soapy water solution around the new sensor to verify there are no air leaks.

7. 7

   Clear Codes

   Connect a diagnostic tool to clear fault code 12652 from the ECU, then test the trailer brake pedal actuation to ensure the system operates correctly and the code does not return.