John Deere 000177.09 – SSU / SST: Hydraulic Oil Temperature Message Missing

The Steering System Control Unit (SSU) is not receiving the expected CAN bus message containing hydraulic oil temperature data. This is a communication issue on the vehicle's controller area network (CAN bus) where information from the sending controller is not reaching the SSU. The SSU requires this temperature information for proper operation of systems it manages, such as the AutoTrac™ system, which may be disabled if the oil temperature is perceived as too low. The loss of this message can be caused by high CAN bus traffic, wiring problems, or issues with the sending or receiving control units.

• 9230
• 9330
• 9430
• 9530
• 9630
• 8230T
• 8330T
• 8430T
• 6020
• 6120
• 6220
• 6320
• 6420S

1. 1

   Check for other active or stored fault codes related to CAN bus communication, power supply to other controllers, or the hydraulic temperature sensor circuit

2. 2

   Restart the vehicle to perform a power cycle, which can sometimes resolve temporary communication glitches

3. 3

   Inspect fuses related to the SSU and other relevant controllers (e.g., check fuse F23 for SSU power supply issues)

4. 4

   Visually inspect the CAN bus wiring harness and connectors for damage, corrosion, or loose connections around the SSU, the sending controller, and the hydraulic oil temperature sensor

5. 5

   Check the resistance of the CAN bus terminating resistors with the battery disconnected (measure between pins C and D of the diagnostic connector; ~60 ohms indicates intact resistors, 120 ohms suggests a faulty or disconnected resistor)

6. 6

   Check the hydraulic oil level and ensure the oil cooler is clean and free of debris

7. 7

   Use an infrared thermometer to measure the actual temperature of the hydraulic oil and compare it to display readings to verify sensor accuracy

1. 1

   Address other faults

   If any other CAN bus or power supply-related fault codes are present, diagnose and repair them first before proceeding.

2. 2

   Repair wiring

   If diagnostic checks reveal any damaged wiring or corroded connectors, repair or replace them as necessary. Ensure all connections are clean and secure.

3. 3

   Test the hydraulic oil temperature sensor

   If the wiring appears to be in good condition, test the hydraulic oil temperature sensor and its circuit for correct functionality.

4. 4

   Replace the hydraulic oil temperature sensor

   If the sensor is found to be faulty during testing, replace it with the correct OEM part for your specific machine model.

5. 5

   Address controller issues

   If the fault persists after verifying the wiring and the sensor, the issue may be with the SSU or the control unit that sends the temperature message. Have a qualified technician reprogram or replace the control unit.