Fendt 0A.1.EE – A050 Basic Control Unit ECU (EXT): Trailer brake valve. ABV: bypass output 4 high fault / Y023 solenoid valve faulty

The system detects an electrical fault (such as a short circuit or open circuit) in the Y023 solenoid valve. As a safety consequence, the compressed air pilot control system is automatically switched off.

• 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 200 Vario series (V/F/P)
• Fendt 300 Vario series (COM III)
• Fendt 400 Vario series
• Fendt 700 Vario series
• Fendt 800 Vario series
• Fendt 900 Vario series (COM III)

1. 1

   Locate the Y023 solenoid valve or ABV (hydraulic trailer brake valve) at the rear of the tractor near the power lift or on top of the central control block.

2. 2

   Inspect wiring harness and connector X334 for breaks, corrosion, or a short circuit to +UB (battery voltage) or earth.

3. 3

   Test the Y023 solenoid coil resistance with a multimeter to check for an out-of-spec reading (open loop or zero resistance).

4. 4

   Verify continuity from the A050 Basic Control Unit ECU harness pins to the valve to rule out a broken wire in the main chassis harness.

1. 1

   Depressurize the System

   Safely park the tractor, turn off the engine, and pump the brakes to relieve any residual pneumatic or hydraulic pressure in the trailer brake system.

2. 2

   Disconnect Power

   Disconnect the tractor's battery to prevent electrical shorts or accidental ECU damage during the repair.

3. 3

   Remove the Faulty Component

   Disconnect the X334 electrical connector from the Y023 solenoid valve / ABV trailer brake valve. Carefully disconnect the air/hydraulic lines, noting their positions. Unbolt the valve assembly from its mounting bracket.

4. 4

   Rebuild or Replace

   If rebuilding: Disassemble the valve on a clean workbench. Use an OEM seal kit or valve repair kit to replace all internal O-rings, diaphragms, and the faulty solenoid coil. If replacing: Install the brand-new trailer brake valve assembly.

5. 5

   Reinstallation

   Bolt the valve back onto the tractor. Reconnect the pneumatic/hydraulic lines securely to prevent leaks. Plug in the electrical connector.

6. 6

   Test and Clear Codes

   Reconnect the battery and start the tractor. Build up air pressure and check for leaks with soapy water. Clear the 0A.1.EE fault code using the tractor's terminal or a diagnostic tool (like TEXA or FENDIAS). Test the trailer brake functionality to ensure the bypass output is operating correctly.