Fendt 8.3.33 – A014 - ECU, EPC OBE: Low voltage condition on the power supply circuit for the rear hitch control system

The system has detected that the voltage from Battery 1 (G001) has dropped below the minimum operating threshold (< 11.0 V or < 10.5 V). Because the voltage is too low to safely operate the proportional solenoid valves, the system triggers a protective state, resulting in 'Control barred and locked' or 'Control is continued' with limited functionality.

• 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 300 Vario (COM III)
• Fendt 400 Vario (COM I, II, III) (e.g., 409, 410, 411, 412, 413, 414, 415)
• Fendt 700 Vario (COM I, II, III) (e.g., 711, 712, 714, 716, 718, 724)
• Fendt 800 Vario (COM I, II, III) (e.g., 815, 817, 818, 820)
• Fendt 900 Vario (COM I, II, III) (e.g., 916, 920, 924, 926, 930)

1. 1

   Test Battery 1 (G001) and Battery 2 (if equipped) directly at the posts with a multimeter. Resting voltage should be ~12.6V. Perform a load test to ensure the battery isn't dropping voltage under demand.

2. 2

   Start the engine and check the voltage at the battery. It should read between 13.5V and 14.5V to verify the alternator is charging.

3. 3

   Check the battery terminals, chassis ground straps, and cab ground connections for heavy corrosion or looseness.

4. 4

   Measure the voltage directly at the power input pins of the A014 ECU (Circuit +Ub / Sheet 25). If the battery reads 12V but the ECU is receiving < 11V, there is a wiring harness issue.

5. 5

   Check fuses F040 and F041 supplying the A014 module.

1. 1

   Secure the Tractor

   Park on a level surface, lower the rear hitch mechanically if suspended, turn off the engine, and remove the key.

2. 2

   Clean Electrical Contacts

   Disconnect the battery cables (negative first). Clean the battery posts and cable terminals thoroughly with a wire brush. Reconnect and tighten securely.

3. 3

   Replace Power Source Components

   If the battery failed the load test, replace it. If the alternator is not outputting >13.5V, replace the alternator and inspect the drive belt tension.

4. 4

   Repair the +Ub Harness

   If the voltage drop is isolated to the A014 ECU supply line, trace the wiring harness back from the ECU to the fuse panel/battery. Repair any chafed wires or replace corroded connector pins.

5. 5

   Clear Codes

   Turn the ignition on. Use the tractor's terminal display or the Fendt SERDIA diagnostic software to clear the fault code.

6. 6

   Test Operation

   Verify that the 'Control barred and locked' warning is gone and that the rear power lift raises and lowers normally via the in-cab controls.