John Deere 3599.06 – OIC (Operator Interface Console) / Cab Control Unit: Supply Voltage 3 of the Cab Control Unit, Current Too High

The current draw on the No. 3 supply voltage circuit (or Secondary ELX Output 1) for the cab control unit is excessively high, strongly suggesting a short to ground in that specific supply lead or output circuit.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 8225R
• 8245R
• 8270R
• 8295R
• 8320R
• 8345R
• 8400R
• 9360R
• 9410R
• 9460R
• 9470RT
• 9510R
• 9520RT
• 9560R
• 9570RT
• 7200R
• 7215R
• 7230R
• 7260R
• 7280R
• 6110M to 6195M
• 6110R to 6215R
• 5080G
• 5090G
• 5100G

1. 1

   Visually inspect the wiring harnesses connected to the Cab Control Unit (OIC) for obvious signs of chafing, rubbing, melting, or pinched wires, particularly where the harness routes through the cab firewall or near metal brackets.

2. 2

   Disconnect the battery and the harness from the OIC module to isolate the circuit.

3. 3

   Using a multimeter, check the resistance to ground on the pin(s) corresponding to Supply Voltage 3 (or Secondary ELX Output 1). A reading of near zero ohms indicates a hard short to ground in the wiring harness.

4. 4

   If the circuit powers specific secondary cab accessories (ELX outputs), disconnect those accessories one by one to see if the short goes away, isolating the short to a connected component rather than the wiring.

5. 5

   If the wiring harness and all connected components test perfectly fine (no short to ground), check if the internal circuitry of the OIC module itself has failed and is shorting internally.

1. 1

   Power Down

   Turn off the tractor key switch and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Access the Harness

   Remove the necessary cab interior trim panels to access the OIC / Cab Control Unit and its main wiring connectors.

3. 3

   Repair the Wiring

   If a short is found in the harness, trace the Supply Voltage 3 / ELX Output 1 wire from the OIC connector to its destination. Locate the damaged section of the wire, cut it out, and splice in a new piece of wire using OEM-approved weather-sealed crimp connectors or solder/heat-shrink. Re-wrap the harness with protective loom and secure it away from sharp edges.

4. 4

   Replace the OIC Module

   If the module is internally shorted, unplug all connectors from the OIC, unbolt the module from its mounting bracket, install the new OIC module, and reconnect the harnesses. Note: A new OIC / Cab Control Unit will likely require programming/calibration via John Deere Service ADVISOR to match the tractor's specific configuration.

5. 5

   Test

   Reconnect the battery, turn the key on, and clear the stored fault codes. Operate the tractor's cab functions to verify the code 003599.06 does not return.