CLAAS Id7621h / 7621h (402) – TR2 (A57-2): Pressure of high-pressure brakes < 70 bar during < 2 seconds, during operation

Hydraulic pressure in the high-pressure braking circuit has dropped below the minimum safe operating threshold of 70 bar for a brief period (under 2 seconds) while the machine is running. This condition triggers a blinking brake indicator light on the dash, though it does not trigger an audio warning.

• CLAAS Axion series (e.g., Axion 810, 850, 920, 950, 8x0 CMATIC)
• CLAAS Arion series (e.g., Arion 410, 420, 430, 510, 610, 630, 640, 650)

1. 1

   Hydraulic Circuit Inspection: Check the service brakes hydraulic circuit for physical leaks, damaged pipes, or faulty selector valves.

2. 2

   Sensor Consistency: Check the high-pressure braking pressure sensor 1 (Component B368, located on the rear brake circuit) for measurement consistency.

3. 3

   Solenoid Valve Check: Test the high-pressure braking solenoid valve (Component Y329) to ensure it is opening correctly and receiving proper power supply.

4. 4

   Accumulator Check: Inspect the rear service brake pressure accumulator (Component 5063) to ensure it is inflating properly when the brake pedals are depressed.

5. 5

   Electrical & Harness Check: Check the voltage delivered by the transformer (Component V24). Verify the continuity, power supply, and signal of the wiring harnesses and connectors for all aforementioned components.

6. 6

   Module Testing: Test the "Auto 5" electronic control unit using the specific CLAAS diagnostic tool/harness.

1. 1

   Initial Reset

   Restart the vehicle. The error code is designed to disappear automatically when the pressure in the rear brake circuit rises above the accumulator inflation start threshold during the brakes applied and accumulators reinflation phases.

2. 2

   Visual & Multimeter Testing

   If the error persists after a restart, visually inspect the brake hydraulic lines. Use a multimeter to verify the voltage at the V24 transformer and the wiring harnesses for the B368 pressure sensor and Y329 solenoid valve.

3. 3

   Component Replacement

   If the B368 sensor is providing erratic readings or the Y329 solenoid is failing to open/close, replace the faulty component.

4. 4

   Accumulator Service

   If the hydraulic circuit is intact but pressure drops rapidly, the rear service brake pressure accumulator (5063) may have failed and will need to be replaced or recharged.

5. 5

   Auto 5 Module Replacement

   Connect the "Auto 5" diagnostic tool (Part No. 60 05 033 249) to the Auto 5 module. If the module fails the diagnostic test, it must be replaced.

6. 6

   Post-Repair Validation

   After repair, restart the tractor and apply the brakes for at least 2 seconds during the accumulators reinflation phase (outside of the initialisation phase) to ensure the system holds pressure above 70 bar and the code clears.