Fendt A.1.5E – A057 - ECU, steering controller (Auto-Guide): Supply voltage is < 10.1 VDC

The supply voltage to the Auto-Guide steering controller is below the required 10.1 VDC threshold, which is necessary to operate the automated steering valves and sensors safely.

• 411 Vario COM III
• 412 Vario COM III
• 413 Vario COM III
• 414 Vario COM III
• 415 Vario COM III
• 712 Vario COM III
• 714 Vario COM III
• 716 Vario COM III
• 718 Vario COM III
• 818 Vario COM III
• 820 Vario COM III
• Fendt 200 Vario series (207, 208, 209, 210, 211)
• Fendt 300 Vario (COM III)
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III)
• Fendt 800 Vario (COM III) (including 820 Vario greentec)
• Fendt 900 Vario (COM III)

1. 1

   Check the tractor's base battery voltage (must be above 12V) and ensure the alternator is charging properly under load.

2. 2

   Inspect the fuse panel for blown fuses or sticking relays that supply power to the Auto-Guide circuit.

3. 3

   Inspect the main harness routing to the A057 ECU for chafing, pin corrosion, or loose ground connections (refer to Wiring Diagram Sheet 39).

4. 4

   Disconnect the A057 ECU connector (X1716) and measure voltage across power and ground pins (4, 28, and 39) with the key ON to verify it is above 10.1 VDC.

1. 1

   Isolate the Power Loss

   If the voltage at connector X1716 is below 10.1 VDC, trace the circuit back through the cab wiring harness using Sheet 39 of the wiring diagram.

2. 2

   Repair Wiring

   Repair any broken wires, clean corroded connector pins, and secure all chassis grounds related to the steering controller.

3. 3

   Test the ECU

   Reconnect the A057 ECU and turn the ignition ON. If the voltage drop is only present when the ECU is plugged in, the module may have an internal short.

4. 4

   Address Internal Faults

   If the voltage is corrected but the system now throws code A.1.5F (A057 - Internal fault) or A.1.56 / A.1.57 (EEPROM reading/invalid data faults), the A057 ECU has failed and must be replaced.

5. 5

   Reprogramming

   If the A057 box is replaced, you must perform EOL (End of Line) programming using the FENDIAS diagnostic tool to write the correct tractor parameters to the new EEPROM.

6. 6

   Calibration

   After repair or replacement, restart the Auto-Guide calibration mode at a standstill to ensure the steering valve and steering angle sensors are synchronized.