CLAAS Id7639h / 7639h (426) – TR2 (A57-2) Transmission Control Module: Error on high pressure braking

Triggered when the pressure in the high-pressure braking circuit drops below 70 bars for a duration of 0.2 to 2 seconds during operation. The system's programmed safety response to this condition is to run the hydraulic pump for 15 seconds and prompt the operator to restart the tractor.

• CLAAS Axion 800 Series (e.g., 810, 850)
• CLAAS Axion 900 Series (e.g., 920, 950, 960)
• CLAAS Arion 500 & 600 Series (e.g., 510, 530, 550, 620, 640, 650)

1. 1

   Verify actual physical pressure in the braking circuit and compare it with the high-pressure braking pressure sensor reading to ensure measurement consistency.

2. 2

   Inspect the high-pressure braking solenoid valve for correct opening operation and verify its power supply.

3. 3

   Check the entire service brakes hydraulic circuit for leaks, paying special attention to the decompression screw, non-return valves, pipes, and selectors.

4. 4

   Inspect the rear service brake pressure accumulator to ensure it is not torn and is properly holding a charge.

5. 5

   Inspect wiring harnesses and connectors for the sensor and solenoid valve for continuity, proper power supply, signal integrity, short-circuits, or open circuits.

6. 6

   Check the voltage delivered by the transformer (V24) and, if necessary, check the 'Auto 5' module using CLAAS diagnostic tool n° 60 05 033 249.

1. 1

   Restart and Re-evaluate

   The system will attempt to pump for 15 seconds. Restart the vehicle. If the error code disappears when the pressure in the rear brake circuit rises above the accumulator inflation start threshold, it may have been a temporary pressure drop.

2. 2

   Address Leaks

   If the error persists, repair any physical leaks found in the hydraulic braking circuit during the diagnostic phase.

3. 3

   Replace Faulty Components

   If the actual circuit pressure is fine but the sensor reads incorrectly, replace the pressure sensor. If the solenoid valve fails to open or the accumulator cannot hold pressure, replace the respective component.

4. 4

   Clear Codes

   Clear the error codes from the TR2 module.

5. 5

   Test Drive

   Operate the tractor, applying the brakes to force the accumulators to reinflate. Ensure the pressure remains above the 70-bar threshold and the code does not return.