John Deere CCU000096.03 – C03: Fuel Level Sensor Voltage Above Normal

The Cornerpost Control Unit (C03) has detected an abnormally high voltage signal from the fuel level sensor circuit (SPN 96, FMI 03). This indicates that the circuit is experiencing a voltage above normal or is shorted to a high power source. This fault typically causes the fuel gauge to read full regardless of the actual fuel level in the tank.

• 6115M
• 6M Series
• 6R Series
• 9560 STS
• 9660 STS
• 9760 STS
• 9860 STS
• 9560 WTS
• 9660 WTS
• 9760 WTS
• 9860 WTS
• 9750 STS
• 9870 STS
• 9660CTS
• 4000 Series Sprayers
• 8000 Series Tractors

1. 1

   Visually inspect the wiring harness running from the fuel tank sending unit to the Cornerpost Control Unit for pinched, chafed, or melted insulation.

2. 2

   Unplug the connector at the fuel tank and inspect for green or white corrosion, moisture, or bent pins.

3. 3

   Check the ground strap for the fuel sending unit or fuel tank to ensure it is securely fastened to the frame and free of rust or corrosion.

4. 4

   Test for a short to power: disconnect the fuel level sensor connector, turn the key to the 'ON' position, and use a multimeter to measure voltage between the signal wire pin at the harness connector and a known good chassis ground.

5. 5

   Test the fuel level sensor (sending unit) resistance: disconnect the sensor, connect a multimeter (set to Ohms) to the signal and ground pins, and slowly move the float arm from empty to full. The resistance should change smoothly without dropouts or 'OL' (Over Limit) readings.

1. 1

   Confirm fault code

   Access the diagnostic trouble codes through the machine's monitor to confirm C03 96.03 is active before proceeding with repairs.

2. 2

   Perform Diagnostics

   Follow the diagnostic checks outlined above to isolate the root cause (wiring, ground, or sensor).

3. 3

   Repair wiring harness

   If a short to power or physical damage is found during inspection, repair the damaged section using weatherproof connectors and heat-shrink tubing. Clean or replace severely corroded connectors.

4. 4

   Repair ground connection

   If the ground connection is found to be faulty or corroded, remove the ground strap, clean both contact points to bare metal, and re-secure it tightly.

5. 5

   Replace fuel sending unit

   If the sensor resistance test shows erratic readings, no change, or 'OL', replace the sending unit. Clean the area around the tank, disconnect electrical and fuel lines, unscrew the retaining ring/bolts, and install the new unit ensuring the gasket is properly seated.

6. 6

   Final verification

   Reconnect the battery, turn the key to the 'ON' position, clear the fault codes using the machine's display, and verify that the fuel gauge provides an accurate reading and the code does not return.