John Deere 5126.03 – ECU: Sensor Supply Voltage 8 Out of Range High / Sensor Supply Voltage Too High, Exhaust Pressure Sensor, Engine Oil Pressure Sensor

This diagnostic trouble code indicates that the 5-volt supply voltage for "Sensor 8" (which powers the Exhaust Pressure Sensor and Engine Oil Pressure Sensor) is out of range high. This typically indicates a short circuit to a 12V power source on the sensor supply circuit.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5090M
• 5095M
• 5095MH
• 5105M
• 8310RT
• 8335RT
• 8360RT
• 8245R through 8400R

1. 1

   Visually inspect the wiring harnesses and connectors associated with the Exhaust Pressure Sensor and the Engine Oil Pressure Sensor for damaged, frayed, melted, or loose wiring

2. 2

   Use a multimeter to inspect the Sensor 8 supply circuit for any points where the wires may be shorted to a 12V power source

3. 3

   Disconnect the Exhaust Pressure Sensor and Engine Oil Pressure Sensor one at a time; if the voltage returns to the normal 5V range when a specific sensor is unplugged, that sensor is internally shorted

4. 4

   Ensure that the electrical supply originating from the ECU to the sensor is stable and within the correct 5V specification

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent electrical damage during repairs.

2. 2

   Repair Wiring

   If the diagnostic checks revealed frayed wires or a short to 12V in the harness, repair or splice the damaged wiring and insulate it properly. Replace any corroded or damaged connector pigtails.

3. 3

   Replace Faulty Sensor(s)

   If the wiring is intact but one of the sensors tested as internally shorted, remove and replace the faulty Exhaust Pressure Sensor or Engine Oil Pressure Sensor.

4. 4

   Reassemble and Reconnect

   Reconnect all sensor harnesses and reconnect the battery.

5. 5

   Reset ECU and Monitor

   Turn the key to the ON position. Use a diagnostic tool to clear the 005126.03 fault code from the ECU. Start the engine and monitor the system to ensure the code does not return and the sensors are reading accurately.