Fendt 0A.1.ED – Tractor Main Control Unit / Dashboard Control Module: Trailer brake control circuit malfunction

Fault code 0A.1.ED indicates a malfunction within the trailer brake control circuit. It means either the A128 control panel for right/left dashboard ABV activation button is faulty, or there is a trailer brake valve ABV bypass output 2 low fault associated with the Y173 trailer brake release solenoid valve.

• 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 V/F/P Vario Series (207, 208, 209, 210, 211)
• Fendt 300 Vario Series
• Fendt 400 Vario Series
• Fendt 700 Vario Series
• Fendt 800 Vario Series
• Fendt 900 Vario Series
• 711
• 714
• 716
• 815
• 818
• 916
• 924
• 930
• 936

1. 1

   Inspect the A128 Control Panel: Test the ABV (trailer brake) activation button on the right/left dashboard for physical damage, sticking, or internal failure. Use a multimeter to check for proper continuity when pressed.

2. 2

   Check the Y173 Solenoid Valve: Locate the trailer brake release solenoid valve (Y173). Test the solenoid coil for proper resistance and ensure it is not shorted to ground.

3. 3

   Inspect the Wiring Harness: Trace the wiring between the A128 control panel, the main ECU, and the Y173 solenoid valve. Look for pinched wires, breaks, or corroded connectors that would cause a low fault or signal interruption.

4. 4

   Verify Power Supply: Check the 12V supply and relevant fuses (e.g., fuse 30) that power the trailer brake circuit.

1. 1

   Disconnect Power

   Disconnect the tractor's battery to prevent electrical shorts during repair.

2. 2

   Address the Dashboard Switch (If Faulty)

   If diagnostic checks reveal the A128 ABV activation button is faulty, carefully remove the dashboard trim panel, unplug the switch connector, and replace the faulty switch/panel component.

3. 3

   Repair Wiring

   If the wiring harness between the cab and the Y173 solenoid is damaged, splice and heat-shrink the broken wires or replace the damaged connector pins.

4. 4

   Replace the Solenoid/Valve (If Faulty)

   If the Y173 solenoid valve has failed internally, relieve any residual hydraulic/pneumatic pressure in the brake lines. Unbolt the solenoid from the trailer brake valve assembly and install the replacement. If the valve body itself is leaking or seized, rebuild it using an OEM repair kit or replace the entire trailer brake valve assembly.

5. 5

   Reassemble and Reconnect

   Reconnect the battery and turn the ignition on.

6. 6

   Clear Codes

   Connect the FENDIAS or SERDIA diagnostic tool to the tractor and clear the 0A.1.ED fault code from the system's memory.

7. 7

   Functional Test

   Actuate the handbrake and the ABV button to ensure the trailer brake releases properly and the code does not return.