Massey Ferguson P74 – Autotronic 5: X21 - ParkLock brake pressure sensor: Pressure too low.

The system has detected that the hydraulic pressure within the ParkLock (park brake) circuit has dropped below the minimum required threshold to safely hold or release the parking brake mechanism.

• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• Interim Tier 4 (2012-2015)
• 8650
• 8660
• 8670
• 8680
• 8690

1. 1

   Verify the transmission/hydraulic oil level is correct and the filters are not blocked (which can starve the ParkLock circuit of pressure).

2. 2

   Locate the X21 ParkLock brake pressure sensor. Inspect the wiring harness and connector for chafing, corrosion, or a loose connection.

3. 3

   Plumb a mechanical hydraulic pressure gauge into the ParkLock test port. Compare the actual physical pressure against the reading the X21 sensor is sending to the Autotronic 5 controller.

4. 4

   Inspect the ParkLock filling and bleed solenoid valves for sticking or internal bypassing, which could cause a legitimate low-pressure situation.

1. 1

   Depressurize

   Turn off the engine, engage the wheel blocks, and cycle the hydraulic valves to relieve residual system pressure. Disconnect the battery.

2. 2

   Locate the Sensor

   Locate the X21 ParkLock brake pressure sensor on the transmission/ParkLock hydraulic valve block.

3. 3

   Removal

   Disconnect the electrical harness from the X21 sensor. Carefully unscrew the sensor from the valve block. Have a shop towel ready to catch residual hydraulic fluid.

4. 4

   Installation

   Lubricate the O-ring on the new X21 sensor with clean hydraulic fluid. Thread the new sensor into the valve block and tighten to the OEM torque specification.

5. 5

   Reassembly

   Reconnect the electrical harness. Reconnect the battery.

6. 6

   Calibration/Clearing

   Start the tractor and use a diagnostic tool (such as AGCO EDT or Wintest) to clear the P74 fault code. Test the ParkLock engagement and disengagement to ensure the pressure reads correctly and the tractor holds stationary.