Massey Ferguson T138 – TRANS1: High Pressure Brake System Pressure Too Low

Triggered when the braking pressure drops below 70 bar (1015 psi) during the initialization phase of the 50 km/h (31 mph) high-pressure braking unit.

• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• Interim Tier 4 (2012-2015)
• MF 7600 Series
• MF 6600 Series
• MF 6700 Series
• MF 7700 Series
• MF 8600 Series
• MF 8700 Series
• MF 5400 Series
• MF 6400 Series

1. 1

   Check the tractor's battery voltage and voltage supply, as low voltage can cause false readings (related codes T148 or T149).

2. 2

   Inspect the wiring harness and connector leading to the braking pressure sensor (Sensor B233) for disconnections, corrosion, or short circuits.

3. 3

   Verify actual hydraulic pressure using a mechanical gauge at the high-pressure braking unit. If pressure is above 70 bar (1015 psi), the sensor is faulty. If below, there is a hydraulic issue.

4. 4

   Inspect the high-pressure brake accumulator for a torn diaphragm or failure preventing the system from holding pressure.

1. 1

   Depressurize the System

   Safely park the tractor on level ground, turn off the engine, and pump the brake pedals repeatedly to relieve any residual hydraulic pressure in the high-pressure braking circuit.

2. 2

   Locate the Sensor

   Locate the high-pressure braking unit and identify the brake pressure sensor (B233).

3. 3

   Remove the Faulty Sensor

   Disconnect the electrical harness from the sensor. Carefully unscrew the sensor from the braking unit block.

4. 4

   Install the New Sensor

   Thread the new OEM pressure sensor into the port. Tighten to the torque specifications outlined in your specific model's workshop manual.

5. 5

   Reconnect and Test

   Reconnect the electrical harness. Start the tractor and allow the high-pressure braking unit to initialize. Verify that the T138 code clears from the dash/TRANS1 module and that the system registers pressure above 70 bar (1015 psi).

6. 6

   Replace Accumulator or Rebuild Unit

   If the mechanical pressure was found to be low during diagnostics, you will need to replace the high-pressure brake accumulator or rebuild the high-pressure braking unit instead of replacing the sensor.