CLAAS Id7634h / 7634h (421) – TR2 (A57-2 or A142) Transmission Control Module: Error on high pressure braking.

This fault indicates that the hydraulic pressure in the high-pressure braking circuit has exceeded the maximum allowable threshold during the system's initialization phase. As a safety and system response, the tractor will typically limit engine speed to 300 RPM.

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

1. 1

   Perform a manual system prime by pumping the brake pedals continuously for 15 seconds, then start the tractor to see if the initialization phase clears the code.

2. 2

   Verify that the power supply voltage to the high-pressure braking sensors is between 4.8 V and 6 V.

3. 3

   Measure the actual physical pressure in the braking circuit and compare it with the live data values reported by the high-pressure braking pressure sensors (B368 for the rear circuit, B370 for the front/secondary circuit).

4. 4

   Check the high-pressure braking solenoid valve (Y329) to ensure it is receiving power and opening correctly.

5. 5

   Inspect the service brakes hydraulic circuit for leaks, paying close attention to the decompression screw (6062), non-return valves, pipes, and the selector.

6. 6

   Check the wiring harnesses and connectors for the sensors and solenoid valve for continuity, proper ground, and signal integrity.

7. 7

   Test the TR2 (Auto 5) module using CLAAS diagnostic tool no. 60 05 033 249.

1. 1

   Attempt Reset

   With the engine off, pump the brake pedal for 15 seconds. Start the tractor. If the code clears and full engine RPM is restored, the system may have just needed to bleed/re-inflate the accumulators.

2. 2

   Inspect Wiring

   If the code persists, visually and electrically test the wiring harness leading to the B368/B370 pressure sensors and the Y329 solenoid valve. Repair any damaged wires or corroded pins.

3. 3

   Test/Replace Solenoid Valve

   Apply direct voltage to the Y329 high-pressure braking solenoid valve. If it fails to actuate or is mechanically stuck closed (causing pressure to spike during initialization), replace the valve.

4. 4

   Test/Replace Pressure Sensor

   If the actual hydraulic pressure is normal but the ECU is reading an over-pressure state, the B368 or B370 pressure sensor has failed internally. Replace the faulty sensor.

5. 5

   Replace Accumulator

   If the system is over-pressurizing due to a lack of expansion volume, the rear service brake pressure accumulator (5063) may have a ruptured internal diaphragm and will need to be replaced.

6. 6

   Replace TR2 Module

   If all sensors, valves, and wiring test perfectly, the TR2 Transmission Control Module (A57-2 / A142) is faulty. Replace the module and flash it with the correct software for the tractor.