John Deere 520572.04 – Rear Chassis Module (PLC): Transmission Output Speed Sensor Low Voltage Direct Drive

The control unit has detected an excessively low voltage at the signal input from the sensor. This typically points to a short to ground in the sensor circuit, a damaged wiring harness, or an internally failed sensor that is returning an abnormally low voltage signal.

• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R

1. 1

   Inspect the Sensor Circuit for Shorts: Trace the wiring harness from the Transmission Output Speed Sensor back to the Rear Chassis Module (PLC). Look for chafed wires, pinched harnesses, or exposed copper that could be shorting to the tractor's chassis (ground).

2. 2

   Check Connections: Disconnect the sensor and inspect the pins. Ensure all connections are secure, tight, and free of moisture, dirt, or corrosion.

3. 3

   Measure Voltage: Use a multimeter to measure the reference voltage at the sensor connector with the key ON. Then, measure the signal return voltage. If the voltage remains abnormally low despite good wiring, the sensor itself has likely failed internally.

4. 4

   Verify Control Unit Functionality: Ensure the PLC is outputting the correct reference voltage. If the module is not sending voltage to the sensor, the issue may lie with the PLC or its main power supply.

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the Transmission Output Speed Sensor on the transmission housing (typically near the output shaft/rear axle housing area).

3. 3

   Disconnect

   Unplug the electrical connector from the sensor.

4. 4

   Remove the Sensor

   Clean the area around the sensor to prevent dirt from falling into the transmission. Remove the retaining bolt(s) and carefully pull the sensor straight out of the housing.

5. 5

   Install the New Sensor

   Lightly lubricate the O-ring on the new sensor with clean transmission hydraulic fluid. Insert the sensor into the port and seat it fully.

6. 6

   Secure

   Install and tighten the retaining bolt to the OEM torque specification.

7. 7

   Reconnect

   Plug the electrical connector back into the sensor, ensuring the locking tab clicks into place.

8. 8

   Test

   Reconnect the battery. Use a diagnostic tool to clear the 520572.04 fault code from the PLC. Start the tractor and test drive it to ensure the transmission shifts correctly and the code does not return.