Understanding and Troubleshooting Auto Throttle on the Komatsu EX120-2 Excavator

[MikePhua]

The Komatsu EX120-2 is a popular hydraulic excavator known for its reliability and efficient performance. One of its key features is the auto throttle system, designed to optimize engine speed and fuel consumption based on operational demands. This article provides an overview of the EX120-2 auto throttle system, common issues, diagnostic tips, and practical advice for maintenance and repair.
What is Auto Throttle?

• The auto throttle automatically adjusts engine RPM according to hydraulic load and operational needs.
  
• It increases engine speed when more power is required (e.g., digging or lifting).
  
• It reduces engine speed during idle or low-load conditions to save fuel and reduce emissions.
  
• Enhances operator comfort by maintaining consistent performance without manual throttle adjustments.
  

Common Auto Throttle Symptoms and Issues

• Engine RPM not increasing under load, causing sluggish performance.
  
• Engine revving unexpectedly or surging without operator input.
  
• Auto throttle failing to engage, remaining at idle speed.
  
• Warning lights or fault codes related to engine control systems.
  
• Unusual noises or vibration linked to throttle system components.
  

Possible Causes

• Faulty throttle position sensors or engine control module (ECM).
  
• Wiring harness damage or poor electrical connections.
  
• Malfunctioning hydraulic pressure sensors.
  
• Software glitches or outdated ECM firmware.
  
• Mechanical problems in the throttle actuator or linkage.
  

Diagnostic and Repair Steps

• Check for error codes using Komatsu diagnostic tools or compatible scanners.
  
• Inspect wiring and connectors for corrosion, damage, or loose connections.
  
• Test throttle position sensors and hydraulic pressure sensors for proper operation.
  
• Verify ECM firmware version and update if necessary.
  
• Inspect and clean throttle actuator components; replace if worn or defective.
  
• Perform a system reset or calibration as per manufacturer instructions.
  

Terminology Explanation

• ECM (Engine Control Module): The computer managing engine functions including throttle control.
  
• Throttle Position Sensor: Sensor detecting the position of the throttle valve to regulate engine speed.
  
• Hydraulic Pressure Sensor: Measures system pressure to determine load demand.
  
• Actuator: A mechanical device that moves or controls a mechanism, such as the throttle valve.
  

Real-World Example
An EX120-2 operator reported the machine’s engine RPM would stay low despite heavy digging demands, resulting in reduced productivity. Technicians found a faulty throttle position sensor causing incorrect feedback to the ECM. After replacement and recalibration, the auto throttle resumed normal function, restoring efficient performance.
Best Practices for Maintaining Auto Throttle Systems

• Regularly inspect electrical connectors and sensors for wear or corrosion.
  
• Keep software and firmware updated according to manufacturer advisories.
  
• Train operators to recognize early signs of throttle system irregularities.
  
• Include auto throttle checks in routine maintenance schedules.
  

Industry Perspective
Auto throttle systems are becoming standard in modern excavators to improve fuel efficiency and reduce emissions. While generally reliable, they require periodic attention to sensors and control units to ensure optimal operation.
Conclusion
The auto throttle feature on the Komatsu EX120-2 significantly enhances machine efficiency by automatically adjusting engine speed to load demands. Understanding common issues and maintenance procedures helps operators and technicians keep this system functioning smoothly, minimizing downtime and maximizing productivity.