CLAAS Id75C3h / 75C3h (304) – TR1 (A57-1): Supply voltage measured on the reverse gear solenoid valve when the driver is not controlled (setpoint PWM = 0).

The transmission control system is detecting electrical voltage on the reverse gear solenoid valve circuit even though the controller is not actively commanding the valve to open (the Pulse Width Modulation [PWM] signal is set to 0). This indicates an unintended voltage supply, which is typically caused by a short circuit to 12V in the wiring harness or an internal failure within the control module itself.

• CLAAS Axion 800 Series (e.g., Axion 810, 850)
• CLAAS Arion 600 and 500 Series (e.g., Arion 640, 630, 610, 510)
• CLAAS Arion 400 Series (e.g., Arion 430, 420, 410)

1. 1

   Inspect the reverse gear solenoid valve power supply harness for a possible 12V short circuit (e.g., chafed wires touching a power source).

2. 2

   Test the "Auto 5" transmission module (TR1 / A57-1) using the official CLAAS diagnostic breakout tool (Tool No. 60 05 033 249) to see if the module is internally shorted and leaking voltage to the output pin.

3. 3

   Check the resistance of the reverse gear solenoid valve winding to ensure it is within specification and not internally shorted.

1. 1

   Preparation

   Safely park the tractor, turn off the engine, and engage the parking brake.

2. 2

   Locate the Component

   Locate the reverse gear solenoid valve on the transmission valve block. In CLAAS wiring diagrams, this is designated as component Y328 (Proportional reverse gear solenoid valve - PSVR).

3. 3

   Test the Harness

   Disconnect the wiring harness from the Y328 solenoid valve. Turn the tractor key to the ON position (do not start the engine and do not select reverse). Use a multimeter to probe the supply pin on the harness connector. If 12V is present, there is a short to power in the circuit.

4. 4

   Trace the Wiring

   If voltage is found, trace the wiring harness back to the TR1 (A57-1) Auto 5 module. Look for melted insulation, pinched wires, or chafing against the chassis. Repair or replace the damaged section of the harness if a physical short is found.

5. 5

   Test the Control Module

   If the wiring harness is completely intact and no external short is found, connect the CLAAS diagnostic tool (Tool No. 60 05 033 249) to the Auto 5 module. This tool helps isolate whether the module itself has failed internally and is sending uncommanded voltage.

6. 6

   Replace the Module

   If the diagnostic tool confirms the module is at fault, replace the TR1 (A57-1) Auto 5 module.

7. 7

   Finalize

   Reconnect all components, clear the fault codes using the CLAAS Diagnostic System (CDS), and perform an operational test to ensure the reverse gear engages properly and the code does not return.