Why Does the JCB JS220 Decelerate While Tracking

[MikePhua]

The Rise of the JCB JS220
The JCB JS220 tracked excavator, introduced in the early 2010s, was part of JCB’s push to modernize its heavy-duty excavator lineup. With a 173-horsepower engine and an operating weight of approximately 22 metric tons, the JS220 was designed for high productivity in demanding environments such as quarrying, infrastructure, and demolition. JCB, founded in 1945 in Staffordshire, England, had already become one of the world’s leading construction equipment manufacturers, with over 300 different models and a global footprint spanning more than 150 countries.
The JS220 featured a Tier 4-compliant engine, advanced hydraulic control, and a robust undercarriage built for long-term durability. Its popularity surged in Europe and Asia, with thousands of units sold within the first few years of release. The machine’s reputation for fuel efficiency and operator comfort made it a favorite among contractors seeking a balance between power and precision.
Symptoms of Deceleration During Tracking
One of the more perplexing issues reported by operators is unexpected deceleration while tracking. This typically manifests after 20–30 minutes of operation and includes:

• Gradual loss of travel speed
  
• Engine RPM remaining stable while hydraulic response fades
  
• Recovery of power when other hydraulic functions are activated (e.g., stick or bucket movement)
  
• No active fault codes except for unrelated sensor alerts
  

This behavior can be frustrating, especially when the machine performs flawlessly during initial operation but loses momentum mid-shift.
Potential Causes and Diagnostic Pathways
The deceleration issue is often linked to the hydraulic control logic and sensor feedback systems. Key suspects include:

• Hydraulic Temperature Sensor Fault
  Even if the sensor has been faulty for years, its absence or incorrect readings can affect the ECU’s logic. The system may interpret high hydraulic temperatures and reduce pump output to protect components.
  
• Shuttle Valve and Travel Pilot Signal Loss
  The JS220 uses a shuttle valve block that detects pilot pressure from travel levers. If the signal is weak or intermittent, the ECU may assume tracking is not being requested and reduce flow. This can be traced by following the pilot hoses to the shuttle valve and inspecting the associated pressure switch.
  
• ECU Misinterpretation of Load Demand
  The electronic control unit may prioritize other hydraulic functions over travel if it receives conflicting signals. Activating the stick or bucket can temporarily restore travel pressure, suggesting a logic conflict rather than a mechanical fault.
  
• Contaminated Hydraulic Fluid or Blocked Filters
  Dirty fluid or clogged pilot filters can reduce signal pressure, leading to sluggish response. Regular fluid analysis and filter replacement are essential.
  
• Software Calibration Drift
  Over time, control parameters may drift due to voltage fluctuations or sensor aging. Recalibrating the ECU and updating firmware can restore proper behavior.
  

Operator Anecdotes and Field Cases
In 2021, a contractor in Malaysia reported that their JS220 slowed down during trenching operations. After replacing the hydraulic temp sensor and cleaning the shuttle valve block, the issue persisted. A technician eventually discovered that the pilot pressure switch was corroded internally, causing intermittent signal loss. Replacing the switch resolved the problem entirely.
Another case in Poland involved a JS220 used for riverbank reinforcement. The operator noticed that travel speed dropped after 40 minutes of use but returned when the boom was moved. The root cause was traced to a software glitch in the ECU that failed to prioritize travel under certain load conditions. A firmware update from JCB restored normal operation.
Terminology Notes

• Shuttle Valve: A hydraulic component that selects between multiple pressure sources, often used to detect pilot input.
  
• Pilot Pressure: Low-pressure hydraulic signals used to control high-pressure valves and actuators.
  
• ECU (Electronic Control Unit): The onboard computer that manages engine and hydraulic functions based on sensor input.
  
• Hydraulic Temp Sensor: A sensor that monitors fluid temperature and informs the ECU to adjust pump output accordingly.
  

Preventative Measures and Recommendations
To avoid deceleration issues in the JS220, operators and technicians should consider the following:

• Replace faulty sensors even if they seem unrelated to current symptoms
  
• Inspect pilot hoses and shuttle valve blocks for leaks or wear
  
• Clean or replace pilot pressure switches regularly
  
• Update ECU firmware during scheduled maintenance
  
• Use OEM hydraulic fluid and filters to maintain system integrity
  
• Log operational anomalies and correlate them with environmental conditions
  

For machines operating in humid or dusty environments, sealing electrical connectors and using corrosion-resistant fittings can prevent signal degradation. Additionally, installing diagnostic tees in pilot lines allows for real-time pressure monitoring during operation.
Modern Comparisons and Design Evolution
Newer JCB models such as the JS235 and JS300 have adopted more advanced hydraulic logic and sensor arrays, reducing the likelihood of signal misinterpretation. These machines feature CAN-bus communication and integrated diagnostics, allowing for faster fault tracing and more precise control.
However, the JS220 remains a reliable and capable machine when properly maintained. Its mechanical simplicity and robust design make it ideal for owner-operators and mid-size contractors who value uptime and serviceability.
Conclusion
Deceleration while tracking in the JCB JS220 is often a symptom of deeper communication issues between pilot inputs and hydraulic control logic. By understanding the interplay between sensors, shuttle valves, and ECU behavior, operators can diagnose and resolve these issues efficiently. In the world of heavy equipment, smooth tracking isn’t just a convenience—it’s a sign that every system is working in harmony.