John Deere CAB001079.04 – CAB: CAB Supply Voltage Problem

The system has detected an issue with the power supply voltage supplied to a specific controller, falling outside the expected operational range (either too high or too low). This can be triggered by sensor supply voltage dropping below thresholds (e.g., below 4.8V on a CCU, or below 0.5V on a 5V supply indicating a short to ground) or low battery voltage during engine cranking (e.g., dropping to 9.4V). This condition may affect the proper operation of the connected components.

• 6105R
• 6115R
• 6125R
• 6130R
• 6140R
• 6150R
• 6150RH
• 6170R
• 6190R
• 6210R
• 7630
• 7730
• 7830
• 7930
• 8130
• 8225R
• 8230
• 8245R
• 8270R
• 8295R
• 8295RT
• 8320R
• 8320RT
• 8330
• 8345R
• 8345RT
• 8430
• 8530
• 9230
• 9330
• 9430
• 9430T
• 9530
• 9530T
• 9630
• 9630T
• 444J
• 544J
• 624J
• 644J
• 724J
• 744J
• 824J
• 844J

1. 1

   Check battery voltage (should be at least 12.6V fully charged) and monitor for significant drops during cranking (e.g., dropping to around 9.4V)

2. 2

   Inspect the alternator and its connections for any visible damage or debris, and ensure the auxiliary drive belt is tight and not slipping

3. 3

   Check cab power supply fuses, specifically F15 and F22

4. 4

   Inspect ground connections, battery cables, and smaller 'piggyback' wires for corrosion or high resistance

5. 5

   Examine the cab wiring harness for chafing, rodent damage, or corrosion, particularly under the dash, under the seat, or where the harness may be too tight against the cab frame

6. 6

   Observe if the code triggers under high electrical loads (like turning on lights) or when quickly cycling the ignition switch

1. 1

   Address immediate voltage issues

   If the battery is low, charge it fully or replace it if it fails a load test. If the alternator is not charging correctly, replace the alternator or install a new voltage regulator.

2. 2

   Clean and secure connections

   Disconnect, clean, and securely reconnect all relevant ground straps and power connections, including the main battery terminals and the power feed to the cab.

3. 3

   Repair damaged wiring

   Repair any damaged wires in the harness using solder and heat-shrink tubing rather than butt connectors. In cases of extensive damage, replace the wiring harness.

4. 4

   Check fuse holders

   Inspect maxi-fuse holders for corrosion which can cause voltage drops, and replace the fuse holder if corrosion is present.

5. 5

   Restart and re-evaluate

   Restart the tractor to see if the fault code clears, as cycling the power can reset the control unit and clear a temporary fault.

6. 6

   Seek professional assistance

   If the code persists, have a qualified technician diagnose the Cab Control Unit using John Deere Service Advisor software. Recalibration is necessary if the controller is replaced.