John Deere 1490 – RCU: Feeder House Speed Signal Voltage Low

The signal voltage feedback for the feeder house speed is below the acceptable threshold, specifically less than 0.10 VDC. Logged by the Right Control Unit (RCU) under Failure Mode Identifier (FMI) 04 on circuit cc# 619, this indicates a potential issue with signal integrity, the sensor itself, or the wiring connections providing the feedback.

• S550
• S560
• S660
• S670
• S670H
• S680
• S680H
• S685
• S685H
• S690
• S690H
• S760
• S770
• S780
• S785
• S790
• 9470 STS
• 9570 STS
• 9670 STS
• 9770 STS
• 9870 STS
• 3950
• 3970
• 5730
• 5830
• 6620
• 7720
• 7721
• 8820
• 9500

1. 1

   Visually inspect the feeder house speed sensor (located on the right-hand side of the lower feeder house shaft) and its wiring harness for frayed wires, loose connections, or corrosion.

2. 2

   Check the sensor alignment with the magnetic pickup points or notched wheel on the shaft. Ensure the set screw for the sprocket is tight and the sprocket has not moved.

3. 3

   Verify power supply to the sensor using a multimeter at the connector (with key on and feeder house engaged). Expected voltage is typically 5 VDC or around 8.4 VDC.

4. 4

   Check the continuity of the wiring harness between the sensor and the RCU to rule out open circuits or shorts to ground.

1. 1

   Repair wiring and connectors

   Correct any issues found during the visual inspection. Repair or replace damaged wiring and ensure all connectors are clean and secure.

2. 2

   Adjust sensor alignment

   If misaligned, loosen the sensor mounting, reposition it to the correct distance from the rotating part of the shaft, and retighten.

3. 3

   Trace wiring to RCU

   If no voltage is present at the sensor, trace the wiring harness back to the RCU checking for breaks. If the harness is intact, the RCU may require professional diagnosis.

4. 4

   Replace speed sensor

   If voltage is present at the sensor but the fault code persists, the sensor itself is likely faulty and should be replaced.

5. 5

   Clear codes and calibrate

   After repairs, clear the fault codes. Perform a feeder house speed calibration if required for your model, then operate the machine to verify the fix.