Troubleshooting 2019 CAT 239D3 with Codes 2685-8 and 2686-8

[MikePhua]

A user on panswork forum reported issues with their 2019 CAT 239D3 skid steer, which displayed fault codes 2685-8 and 2686-8. These codes are related to the hydraulic system’s pressure sensor and sensor circuit, preventing the hydraulic system from functioning properly.
Understanding the Fault Codes

• Code 2685-8: This code indicates an abnormality with the hydraulic pressure sensor in the system. The system is unable to achieve the expected pressure, leading to unstable hydraulic performance.
  
• Code 2686-8: This code is related to a problem in the hydraulic pressure sensor circuit, either due to a malfunctioning sensor or an issue with the sensor’s electrical connections.
  

Potential Causes

1. Faulty Pressure Sensor
   The pressure sensor itself may be malfunctioning and unable to accurately detect pressure changes in the hydraulic system, which prevents the system from adjusting pressure as needed.
   
2. Sensor Circuit Issues
   A problem with the sensor’s electrical circuit, such as poor connection or short circuits, can cause incorrect pressure readings and trigger fault codes.
   
3. Hydraulic Pump or Line Issues
   If the hydraulic pump is malfunctioning or there are leaks in the hydraulic lines, the system may fail to reach the required pressure, affecting the entire hydraulic system’s performance.
   
4. Loose Sensor Connections
   If the sensor’s electrical connection is loose or faulty, the signal may not be transmitted properly, leading to errors and fault codes.
   

Troubleshooting and Solutions

1. Inspect the Hydraulic System
   Start by checking the hydraulic system for leaks or damaged lines. Also, ensure that the hydraulic fluid level and quality are correct. Any issues with the hydraulic system should be addressed first.
   
2. Check the Sensor and Circuit
   Inspect the pressure sensor itself to ensure it's functioning correctly. If the sensor is faulty, it should be replaced. Use a multimeter to check the electrical circuit for short circuits, poor connections, or other electrical issues.
   
3. Verify Sensor Connections
   Examine the electrical connections to the sensor for looseness or corrosion. Clean the contacts and ensure a solid connection.
   
4. Test the Hydraulic Pump
   Check whether the hydraulic pump is operating normally and providing adequate pressure. If the pump is malfunctioning, it may need to be repaired or replaced.
   
5. Reset the Fault Codes
   After addressing the potential issues, reset the fault codes using a diagnostic tool or manually. If the issue persists, further professional diagnostics may be required.
   

Conclusion
The appearance of fault codes 2685-8 and 2686-8 on a CAT 239D3 skid steer is typically related to issues with the hydraulic pressure sensor or its electrical circuit. By inspecting the hydraulic system, sensor, sensor circuit, and hydraulic pump, users can diagnose and resolve the issue. Regular maintenance and checks of the hydraulic system can help prevent such faults and ensure the machine operates efficiently.