Bobcat T870 SCR General Pressure Fault

[MikePhua]

The Bobcat T870 is a highly capable track loader, known for its durability and power. However, like all heavy machinery, it may experience technical issues. One common issue that owners may encounter is the SCR (Selective Catalytic Reduction) General Pressure Fault. This issue can cause the machine to operate inefficiently or even result in a complete shutdown if not addressed promptly. Understanding the causes, symptoms, and troubleshooting steps is essential for resolving this problem and maintaining the loader's performance.
Symptoms of SCR General Pressure Fault

1. Loss of Power or Efficiency
   One of the primary symptoms of the SCR general pressure fault is a noticeable drop in engine power or efficiency. The loader may run sluggishly, with reduced torque or speed, particularly when under load.
   
2. Warning Lights or Alerts
   A warning light or alert on the control panel often signals the presence of an SCR fault. This alert is typically accompanied by an error code that can provide more specific information about the problem, helping technicians or operators to identify the issue more quickly.
   
3. Exhaust Emissions Problems
   The SCR system plays a key role in reducing harmful emissions, and when it malfunctions, you may notice an increase in exhaust smoke or the machine failing to meet emissions standards.
   
4. System Shutdown
   In more severe cases, the SCR fault may cause the Bobcat T870 to go into a limp mode or even shut down completely, leaving the machine inoperable until the issue is resolved.
   

Common Causes of SCR General Pressure Fault

1. Low DEF (Diesel Exhaust Fluid) Levels
   One of the most common causes of an SCR pressure fault is low or contaminated DEF levels. The SCR system uses DEF to reduce nitrogen oxide (NOx) emissions, and inadequate DEF can lead to improper function of the system, triggering a pressure fault.
   
2. Clogged or Malfunctioning SCR Sensors
   The SCR system relies on various sensors to measure exhaust pressure and the effectiveness of the DEF injection. If these sensors become clogged, damaged, or fail, they may send incorrect signals to the system, causing a pressure fault.
   
3. Defective SCR Pump
   The SCR system uses a pump to inject DEF into the exhaust system. If the pump fails or becomes clogged, it may not inject the fluid properly, resulting in low pressure and an associated fault.
   
4. Leaking or Blocked DEF Lines
   Leaks or blockages in the DEF supply lines can also lead to insufficient DEF delivery, causing pressure faults. It’s important to inspect the DEF lines for cracks, damage, or blockages that could hinder proper fluid flow.
   
5. Faulty SCR Module or Wiring
   A faulty SCR module or wiring issue can also cause the general pressure fault. The SCR module controls the operation of the DEF system, and any electrical issues may result in incorrect readings or system malfunctions.
   

Troubleshooting SCR General Pressure Fault

1. Check DEF Levels
   Start by inspecting the DEF tank. Ensure that the fluid level is adequate and that it is clean. Contaminated or old DEF fluid can lead to system malfunctions. If the fluid is low, refill it with the recommended grade of DEF fluid.
   
2. Inspect SCR Sensors and Wiring
   Examine the SCR sensors for damage, dirt, or clogging. Clean or replace the sensors as needed. Also, inspect the wiring and connectors for any signs of corrosion, damage, or loose connections, which could be affecting sensor performance.
   
3. Test the SCR Pump
   Check the SCR pump for proper operation. You can do this by monitoring fluid flow or listening for unusual noises from the pump. If the pump is malfunctioning, it may need to be replaced or repaired.
   
4. Examine DEF Lines for Leaks or Blockages
   Inspect the DEF lines for leaks or obstructions. If there are any cracks, holes, or blockages, replace or clean the lines accordingly. Ensure that the lines are clear of any debris that may impede fluid flow.
   
5. Diagnose with Diagnostic Tool
   If the issue persists, use a diagnostic tool to retrieve error codes from the machine’s computer. These codes can pinpoint the specific issue, whether it’s related to the sensors, pump, wiring, or other components of the SCR system.
   

Preventive Maintenance for SCR System

1. Regular DEF Monitoring
   Keep track of DEF levels and ensure that the fluid is clean and free from contamination. Always use the correct DEF fluid to avoid potential system issues. Regularly check the DEF tank and ensure that it remains properly filled.
   
2. Routine Sensor Cleaning and Inspection
   Periodically clean and inspect the SCR sensors. Keeping these components free from dirt and debris ensures that they send accurate readings, which helps the SCR system function optimally.
   
3. Inspect the SCR System Components
   Regularly check the SCR system’s pump, lines, and wiring. Look for any signs of wear or damage and address any issues immediately to prevent more serious failures.
   
4. Follow Manufacturer’s Guidelines
   Always follow the maintenance and service intervals recommended by Bobcat for the SCR system. Adhering to the manufacturer’s guidelines will help prevent premature wear and ensure the system performs as intended.
   

Conclusion
The SCR general pressure fault on the Bobcat T870 can be caused by various issues, including low DEF levels, malfunctioning sensors, and faulty pumps. By following the troubleshooting steps outlined above, operators can identify and resolve the issue quickly. Regular preventive maintenance, such as monitoring DEF levels and inspecting SCR components, will help keep the system in good working order and prevent future faults. Addressing SCR issues promptly is crucial to maintaining the loader's efficiency, performance, and compliance with emissions standards.