Massey Ferguson P55 – Transmission Control Unit (TCU) / TRANS1 / Autotronic 5: X135 - Braking pressure sensor Pressure greater than 230 bar (3336 psi)

The system is detecting that the hydraulic or pneumatic pressure in the braking/ParkLock circuit is dangerously high, exceeding the maximum threshold of 230 bar. Normal operating pressure for the main braking circuit is typically regulated between 135 and 165 bar.

• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• Interim Tier 4 (2012-2015)
• 7400 Series
• 7465
• 7475
• 7480
• 7490
• 7495
• 7600 Series
• 7700 Series
• 7715
• 7718
• 7720
• 7724
• 8400 Series
• 8450
• 8460
• 8470
• 8480
• 8600 Series
• 8650
• 8660
• 8670
• 8680
• 8690

1. 1

   Perform a mechanical pressure test by connecting a gauge to the braking circuit test port to verify if actual pressure exceeds 230 bar (normal is 135-165 bar).

2. 2

   Inspect the wiring harness and connector for the X135 Braking Pressure Sensor for a short to power (+12V), which can cause a falsely high reading.

3. 3

   If mechanical pressure is genuinely too high, inspect the trailer braking proportional solenoid valve (X38), safety solenoid valve (X39), and make-and-break regulator valves for sticking.

1. 1

   Depressurize the System

   Park the tractor on a level surface, turn off the engine, and safely relieve all hydraulic and pneumatic pressure from the tractor's braking and ParkLock systems by pumping the brake pedals until depleted.

2. 2

   Locate the Sensor

   Locate the X135 Braking Pressure Sensor. It is typically threaded into the main braking/ParkLock valve block located on the transmission housing.

3. 3

   Disconnect Wiring

   Carefully unplug the electrical connector from the X135 sensor.

4. 4

   Remove the Sensor

   Using the appropriate wrench, unthread the faulty pressure sensor from the valve block. Have a shop towel ready to catch any residual hydraulic fluid.

5. 5

   Install the New Sensor

   Thread the new OEM pressure sensor into the port and tighten it to the torque specification listed in your specific model's service manual.

6. 6

   Reconnect and Bleed

   Reconnect the electrical harness. If required by the service manual for your specific series, bleed the braking hydraulic circuit to remove any introduced air.

7. 7

   Clear Codes and Test

   Use the AGCO Electronic Diagnostic Tool (EDT) to clear the P55 fault code from the TRANS1 module. Start the tractor, actuate the brakes and ParkLock, and verify that the pressure reads normally and the code does not return.