John Deere 523665.01 – Engine Control Unit (ECU) or PowerShift Transmission Control Unit (PTP): Supply Voltage (BAT) Too Low / ECU Power Circuit #2 Open

The supply voltage to the control unit has dropped below 9 volts, or there is an interruption of the 12V switched power source to the transmission control unit.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5090M
• 5100M
• 5100MH
• 5100ML
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 9470RT
• 9520RT
• 9570RT
• 8245R
• 8400R
• S760
• S770
• S780
• S790
• 7180
• 7280
• 7380
• 7480
• 7580
• 7780
• 7980

1. 1

   Check the battery for adequate charge (system requires a steady voltage above 9V)

2. 2

   Inspect around the batteries and alternator for physical damage, loose grounds, accumulated debris, or corrosion

3. 3

   Check the fuses related to the Engine Control Unit (ECU) or PowerShift Transmission Control Unit (PTP) power circuits

4. 4

   Perform a circuit voltage test (for PTP variants): With ignition in run and engine off, disconnect harness connector (e.g., XA37-2) and verify voltage between the harness extremity (circuit #6212) and frame ground is approximately 12V

5. 5

   Use John Deere Service ADVISOR to test communication between the ECU and Cab Control Unit to ensure voltage supply requests are being received

1. 1

   Clean/Replace Connections

   Disconnect the battery terminals. Clean any corrosion from the battery posts and cable terminals. Reconnect and tighten securely.

2. 2

   Restore Voltage

   If the battery cannot maintain a charge above 9V under load, replace the battery. If the alternator is failing to charge the battery to ~12-14V while running, repair or replace the alternator.

3. 3

   Repair Open Circuits

   If the battery is good but the code persists, trace the ECU Power Circuit #2 (or circuit 6212 for PTP). Look for chafed wires, broken pins, or disconnected harness plugs. Repair any open circuits in the wiring harness.

4. 4

   Replace Blown Fuses

   If the circuit test reveals 0V at the ECU/PTP connector, locate the power distribution box and replace the blown fuse for the respective control unit.

5. 5

   Diagnose CAN/Ground Issues

   If the voltage supply to the control unit is correct (12V) but the system still indicates a problem, diagnose the ground connection or CAN bus wiring for the control unit, as the module may not be grounding properly to complete the circuit.

6. 6

   Clear Codes

   After resolving the voltage drop or open circuit, cycle the key switch, reset the ECU to clear the fault code, and monitor the system to ensure normal operation.