John Deere 002646.03 – SCU: Low Voltage On Rear SCV Valves 1, 2, 5

The system has detected low voltage on rear SCV Valves 1, 2, and 5. This impairs the proper operation of these valves and indicates an issue with the power supply or wiring to the affected circuit, likely stemming from a low voltage supply to the Selective Control Unit (SCU).

• 8120
• 8120T
• 8220
• 8220T
• 8225R
• 8230
• 8235R
• 8245R
• 8260R
• 8270R
• 8285R
• 8295R
• 8295RT
• 8310R
• 8310RT
• 8320
• 8320T
• 8320R
• 8320RT
• 8330
• 8335R
• 8335RT
• 8345R
• 8345RT
• 8360R
• 8360RT
• 8420
• 8420T
• 8430
• 8520
• 8520T
• 8530
• 9120
• 9220
• 9230
• 9320
• 9320T
• 9330
• 9420
• 9420T
• 9430
• 9430T
• 9520
• 9520T
• 9530
• 9530T
• 9620
• 9620T
• 9630
• 9630T

1. 1

   Restart the tractor to see if the fault code clears

2. 2

   Check battery and alternator for damage, corrosion, or debris, and test alternator output to ensure correct charging

3. 3

   Inspect fuses related to the SCU/SCC/SCO (e.g., fuse F29 or F30 on some models)

4. 4

   Reduce electrical load and increase engine RPM to see if the code clears, which would indicate a temporary voltage drop

5. 5

   Carefully examine the wiring harnesses and connectors leading to the SCV control unit and the individual SCV solenoids for damage, corrosion, or loose connections

1. 1

   Isolate the faulty component

   If the fault is intermittent, swap solenoids between different SCV stacks to see if the problem moves with the solenoid. This helps determine if the issue is with a specific solenoid or the wiring/controller.

2. 2

   Test the solenoid

   Test the resistance of the solenoid windings. If the windings are coming apart or the resistance is out of specification, the solenoid must be replaced.

3. 3

   Check controller signal

   Using a multimeter, check for the appropriate voltage signal from the SCV controller to the affected solenoids to determine if the fault lies with the controller or the wiring.

4. 4

   Replace faulty components

   Replace the identified faulty solenoid or the SCV control unit based on the results of the previous tests.

5. 5

   Calibrate the system

   If the SCV control unit was replaced, a calibration by a John Deere dealer may be required.