John Deere 84.04 – CCU (Chassis Control Unit): Wheel Speed Sensor Voltage Issue - Low Voltage

The Chassis Control Unit (CCU) has detected a low voltage condition in the circuit of the rear wheel speed sensor, meaning the voltage reading is below the normal operating range. This fault may affect the accuracy of speed readings and could negatively impact vehicle performance or safety systems.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6210M
• 6090MC
• 6100MC
• 6110MC
• 6090RC
• 6100RC
• 6110RC
• 5075M
• 5090M
• 5100M
• 5115M
• 5125M
• 8245R
• 8270R
• 8295R
• 8320R
• 8345R
• 8R 340
• 8RX 410

1. 1

   Visual Inspection: Locate the wheel speed sensor (usually mounted on the transmission housing, rear axle, or wheel hub) and inspect the wiring harness leading to the sensor for chafing, pinched wires, or melted insulation.

2. 2

   Connector Check: Disconnect the sensor harness and check for water intrusion, bent pins, or corrosion inside the connector.

3. 3

   Voltage/Continuity Test: Turn the key to the ON position (engine off). Using a multimeter, check the reference voltage at the harness connector (typically 5V or 12V) to ensure the CCU is sending proper voltage, and test the ground circuit for continuity.

4. 4

   Sensor Resistance: If the wiring is intact and receiving proper voltage, the sensor itself has likely failed internally and is pulling the voltage down (shorted).

1. 1

   Preparation

   Park the tractor on a level surface, engage the parking brake, turn off the engine, and remove the key.

2. 2

   Locate the Sensor

   Identify the faulty wheel speed sensor on the axle or transmission housing.

3. 3

   Disconnect

   Unplug the electrical connector from the sensor.

4. 4

   Clean the Area

   Thoroughly clean the area around the sensor base with brake cleaner or compressed air to prevent dirt from falling into the housing when the sensor is removed.

5. 5

   Removal

   Remove the retaining bolt holding the sensor in place. Carefully twist and pull the sensor straight out of the bore.

6. 6

   Inspect the Tone Ring

   Shine a flashlight into the mounting hole to inspect the tone ring (the toothed gear the sensor reads). Ensure it is not damaged or covered in excessive metallic debris.

7. 7

   Installation

   Lubricate the O-ring on the new wheel speed sensor with a small amount of clean hydraulic/transmission oil. Insert the new sensor into the bore until it seats fully.

8. 8

   Secure

   Install and tighten the retaining bolt to the manufacturer's torque specification (do not overtighten, as the sensor body is often plastic).

9. 9

   Reconnect

   Plug the electrical harness back into the sensor, ensuring it clicks and locks into place. Secure any loose wiring with zip ties to prevent future chafing.

10. 10

    Clear Codes

    Turn the key on and use the tractor's diagnostic monitor to clear the 000084.04 fault code. Test drive the tractor to verify that the speedometer works and the code does not return.