John Deere 90.04 – CCU: Transmission Hydraulic Oil / Rear PTO Oil Temperature Sensor Low Voltage

A Low Voltage condition in the oil temperature sensor circuit. The controller has detected that the voltage signal from the sensor is lower than the normal expected range, which typically points to a short to ground in the wiring harness or a completely failed sensor.

• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5045E
• 5055E
• 5065E
• 5075E
• 5085E
• 5090E
• 5100E
• 5095M
• 5105M
• 5115M
• 7630
• 7715
• 7720
• 7730
• 7810
• 7815
• 7820
• 7830
• 7920
• 7930
• 9230
• 9330
• 9430
• 9530
• 9630

1. 1

   Turn the key switch to the RUN position (engine off). Check if the code is active. Restart the tractor; sometimes communication messages can be corrected by a simple restart.

2. 2

   Access the CCU diagnostic addresses on the CommandCenter/display to check the live Hydraulic Oil Temperature Sensor Voltage.

3. 3

   Operate the engine at 2200 RPM for 1–2 minutes to see if the code returns.

4. 4

   Thoroughly inspect the sensor's wiring harness and connector for a short to ground, chafed wires, or moisture intrusion.

1. 1

   Power down machine

   Park the machine safely, turn off the engine, and remove the key.

2. 2

   Locate the sensor

   Locate the Transmission Hydraulic Oil or Rear PTO Oil Temperature sensor on the transmission housing or hydraulic sump.

3. 3

   Inspect and test harness

   Disconnect the sensor pigtail and inspect the pins for corrosion or damage. Use a multimeter to verify that the signal wire is not shorted to the ground wire or the chassis.

4. 4

   Replace the sensor

   If the wiring tests good (no shorts) but the CCU still reads a low voltage or shorted value, unthread the old sensor (have a catch pan ready for minor hydraulic fluid loss) and install the new sensor.

5. 5

   Clear codes

   Reconnect the harness, turn the key to the RUN position, and clear the CCU codes.

6. 6

   Test operation

   Start the tractor and operate it to bring the hydraulic oil up to temperature. Verify that code 000090.04 does not return. If the code persists, dealer advanced CCU diagnostics are required.