Takeuchi TB235-2 Throttle Control Issues

[MikePhua]

Introduction
The Takeuchi TB235-2 is a compact, 3.5-ton mini excavator known for its reliability and performance in various construction tasks. Equipped with a Yanmar 3TNV88 engine, it offers 24.4 horsepower at 2,400 rpm and a maximum digging depth of 3,245 mm. Despite its robust design, some operators have reported issues with the throttle control system, particularly the electronic throttle not responding as expected.
Throttle Control System Overview
The TB235-2 utilizes an electronic throttle control system, which allows the operator to adjust engine speed via a dial-type throttle control. This system also features an automatic idle function that reduces engine speed to low idle when the machine is idling for several seconds, enhancing fuel efficiency and reducing engine wear. The throttle system is integrated with the machine's electronic control unit (ECU), which manages engine performance and responds to operator inputs.
Common Throttle Issues

1. Unresponsive Throttle Input
   Some operators have reported that pressing the throttle switch does not result in an increase in engine speed. This issue persists even when the throttle switch appears to be in good condition. Potential causes include:
   • Faulty Throttle Switch: The switch may not be sending the correct signal to the ECU.
     
   • Wiring Issues: Loose or damaged wiring connections can disrupt the signal transmission.
     
   • ECU Malfunction: A malfunctioning ECU may fail to process throttle inputs correctly.
     
2. Throttle Cable Problems
   In some cases, the throttle cable may become damaged or disconnected. For instance, a user reported that the cable controlling the throttle from the auto actuator was broken, causing the throttle to remain unresponsive. Replacing the damaged cable resolved the issue.
   
3. Auto Idle Function Failure
   The auto idle feature, which automatically reduces engine speed when the machine is idling, may stop working if the throttle control system is not functioning properly. This can lead to higher fuel consumption and increased engine wear.
   

Diagnostic and Repair Steps

1. Inspect the Throttle Switch
   • Check for any visible damage or wear on the throttle switch.
     
   • Test the switch for continuity using a multimeter to ensure it is functioning correctly.
     
2. Examine Wiring Connections
   • Inspect all wiring connections between the throttle switch, ECU, and throttle actuator.
     
   • Look for signs of corrosion, loose connections, or damaged wires.
     
3. Test the ECU
   • If the throttle switch and wiring are in good condition, the issue may lie with the ECU.
     
   • Use diagnostic tools to check the ECU for any fault codes or malfunctions.
     
4. Check the Throttle Cable
   • Inspect the throttle cable for any signs of damage or disconnection.
     
   • If the cable is damaged, replace it with a new one.
     

Preventative Maintenance

• Regular Inspections: Conduct regular inspections of the throttle control system, including switches, wiring, and cables, to identify potential issues before they become major problems.
  
• Proper Storage: Store the machine in a clean, dry environment to prevent corrosion and damage to electrical components.
  
• Use Quality Parts: Always use genuine Takeuchi parts for replacements to ensure compatibility and reliability.
  

Conclusion
Throttle control issues in the Takeuchi TB235-2 can stem from various components, including the throttle switch, wiring, ECU, and throttle cable. By systematically diagnosing and addressing these components, operators can restore proper throttle function and maintain the machine's performance. Regular maintenance and prompt attention to any issues can help prevent throttle control problems and ensure the longevity of the TB235-2.