Fendt 04.1.66 – A050 - ECU, basic control unit (EXT): Faulty actuation of the stationary function (high side brake)

The system has detected a faulty actuation of the stationary function (high side brake) due to a fault on the positive (+) side of the Y053 solenoid valve. The electrical signal or voltage supply to the + side of the Y053 valve is interrupted, shorted, or the valve itself is failing to actuate properly. As a result, the active hold/stationary function (engine brake) will not operate.

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• Fendt 300 Vario (COM III)
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III)
• Fendt 800 Vario (COM III)
• Fendt 900 Vario (COM III)
• 916 Vario
• 920 Vario
• 924 Vario
• 926 Vario
• 930 Vario

1. 1

   Inspect the positive (+) side wiring harness leading to the Y053 solenoid valve for line discontinuity, chafing, or corrosion.

2. 2

   Test the K051 Active hold function relay to ensure it is not faulty and that contacts (pins 3 and 5) are not stuck.

3. 3

   Test the Y053 solenoid valve for internal shorts or open circuits by measuring resistance across the valve terminals.

4. 4

   Verify the earth/ground connection to the Y053 valve to rule out ground-side faults.

1. 1

   Locate the Y053 Valve

   On most Vario models (such as the 900 series), the Y053 Active hold function solenoid valve is located on the right side of the transmission. You may need to detach the right rear wheel and access panel to reach it.

2. 2

   Inspect and Repair Wiring

   Disconnect the harness at the Y053 valve (Connector X1041). Use a multimeter to verify voltage from the A050 Basic Control Unit and check for continuity. Repair any broken wires or clean corroded connector pins.

3. 3

   Inspect the Relay

   Locate the K051 Active hold function relay in the electrical panel. Swap it with a known good relay of the same type to see if the fault clears. If the relay was stuck or faulty, replace it.

4. 4

   Replace the Solenoid Valve

   If the wiring and relay are intact but the valve fails electrical testing (or is mechanically seized), remove the retaining hardware, extract the Y053 valve from the transmission block, and install a new OEM solenoid valve.

5. 5

   Clear Codes and Test

   Reconnect all components, turn on the ignition, and use the tractor's terminal to clear the stored 04.1.66 fault code. Perform a stationary brake/active hold test to ensure the function has been restored.