Ride Control Troubles in the 2012 Kawasaki 90Z5: Diagnosis, Activation Logic, and Field Fixes

[MikePhua]

Understanding Ride Control in Wheel Loaders
Ride control systems in wheel loaders like the Kawasaki 90Z5 are designed to dampen hydraulic bounce during travel, especially when the bucket is loaded. This improves operator comfort, reduces material spillage, and minimizes stress on the loader arms and frame. The system typically uses an accumulator charged with nitrogen to absorb shock, and a control valve that activates the system based on speed or manual input.
Terminology Notes

• Ride Control: A hydraulic damping system that smooths loader movement during travel.
  
• Accumulator: A pressure vessel filled with nitrogen that absorbs hydraulic surges.
  
• Activation Logic: The control mechanism—electronic or mechanical—that triggers ride control based on speed or operator input.
  
• Speed Sensor: A device that monitors travel speed and signals the control system.
  
• Solenoid Valve: An electrically actuated valve that opens or closes based on control signals.
  

Symptoms and Observations
Operators of the 2012 Kawasaki 90Z5 reported that while the accumulator and valve were functional, the ride control system failed to activate automatically when the loader reached 4 mph—a threshold where the system is supposed to engage. This pointed to a fault in the activation logic, possibly involving the speed sensor, wiring, or control module.
Common Causes of Ride Control Activation Failure

• Faulty Speed Sensor: If the sensor fails or sends incorrect signals, the system won’t activate.
  
• Disconnected or Damaged Wiring: Electrical faults can prevent the solenoid valve from receiving activation signals.
  
• Control Module Malfunction: The onboard computer may fail to interpret speed data correctly.
  
• Hydraulic Solenoid Failure: Even if the signal is sent, a stuck or burned-out solenoid won’t open the valve.
  

Diagnostic Tips

• Speed Verification: Use a GPS or external speedometer to confirm actual travel speed.
  
• Sensor Testing: Check voltage output from the speed sensor at various speeds.
  
• Solenoid Function Check: Apply direct power to the solenoid to test actuation.
  
• Wiring Inspection: Look for frayed wires, loose connectors, or corrosion near the valve and sensor.
  

Field Anecdotes and Practical Wisdom
One technician shared that after replacing the speed sensor, the ride control began working flawlessly—suggesting the original sensor had degraded over time. In another case, a loader in a cold climate had moisture in the connector housing, which froze and disrupted the signal. After drying and sealing the connector, the issue resolved.
A quarry operator noted that the system could be manually overridden by wiring a switch to the solenoid, allowing ride control to be engaged at will. While not factory-approved, this workaround proved useful during long hauls over rough terrain.
Preventive Measures

• Inspect and clean electrical connectors regularly, especially in wet or dusty environments
  
• Replace speed sensors at recommended intervals or when erratic behavior is observed
  
• Use dielectric grease on connectors to prevent moisture intrusion
  
• Monitor accumulator pressure and recharge nitrogen as needed
  
• Avoid bypassing factory systems unless absolutely necessary and safe
  

Comparative Insight: Ride Control in Other Loaders
In Caterpillar and Volvo loaders, ride control often includes manual override switches and diagnostic codes visible on the display. The Kawasaki 90Z5’s system is simpler but relies heavily on accurate speed sensing. Some newer models use CAN bus communication, allowing technicians to read fault codes directly—an upgrade that could benefit older machines through retrofitting.
Historical Context: The Rise of Ride Control
Ride control systems became standard in the late 1990s as manufacturers responded to operator fatigue and equipment wear. Early systems were manually activated, but speed-based logic improved usability. The Kawasaki 90Z5 reflects this evolution—offering automatic activation but requiring precise sensor input.
Conclusion: A System That Depends on the Invisible
The ride control issue in the Kawasaki 90Z5 wasn’t mechanical—it was a matter of trust between sensors and solenoids. When that trust breaks, the loader feels every bump. Diagnosing such problems requires not just tools, but an understanding of how speed, pressure, and logic converge. As one mechanic put it, “The loader knows when to soften the ride—but only if you teach it to listen.”