John Deere 1079 – C03 / CCU: Concave Position Sensor Supply Voltage Low

The supply voltage for the concave position sensor has dropped below the minimum required threshold of 4.5 VDC (or 4.8 VDC depending on the system). This low voltage condition prevents the sensor from accurately relaying data, which may affect the proper operation of the sensor and the control systems it is part of. The code typically indicates a faulty sensor or an issue within its associated wiring.

• 9540
• 9560
• 9580
• 9640
• 9660
• 9680
• 9560 STS
• 9570 STS
• 9650 STS
• 9660 STS
• 9670 STS
• 9750 STS
• 9760 STS
• 9770 STS
• 9860 STS
• 9870 STS
• S550
• S650
• S660
• S670
• S680
• S690
• 9410
• 9450
• 9510
• 9550
• 9610
• 9650

1. 1

   Review diagnostic trouble codes through the machine's display to confirm the presence of C03 1079.04 or CCU 1079.04

2. 2

   Carefully inspect the wiring harness and connectors between the control unit and the concave position sensor for any visible signs of damage, such as chafing, corrosion, or loose connections

3. 3

   Use a multimeter to test the sensor's voltage levels: confirm the power wire is receiving approximately 5 volts, check for a solid ground connection, and measure the signal voltage to see if it is within the expected range (1 to 4 volts) and changes as the concave position is adjusted

4. 4

   Ensure the machine's battery is in good condition and the charging system is functioning correctly to rule out a systemic low voltage issue

1. 1

   Resolve other codes

   Resolve any other active fault codes, especially those related to CAN bus messages, before addressing this code.

2. 2

   Perform diagnostic checks

   Perform the diagnostic checks listed above to isolate the fault to the sensor, wiring, or control unit.

3. 3

   Repair wiring

   If wiring is faulty, repair or replace the damaged section of the harness.

4. 4

   Replace sensor

   If the sensor is determined to be the cause, replace it with a new one.

5. 5

   Perform calibration

   After replacing the sensor, a Concave Sensor Zero Calibration must be performed. Ensure the concave and separator are clear of any crop material, turn the key switch to the 'RUN' position, enter the diagnostic mode via the in-cab display, navigate to the calibration menu and select the concave calibration option, follow the on-screen prompts to fully close the concave until a clicking sound is heard, and save the new zero setting to complete the calibration.

6. 6

   Clear codes and verify

   Clear the fault code and operate the machine to verify that the repair has been successful.