Steering Control Challenges on the Volvo L120E with CDC System

[MikePhua]

The L120E and Volvo’s Mid-Size Loader Evolution
The Volvo L120E wheel loader was introduced in the early 2000s as part of Volvo Construction Equipment’s E-series, which emphasized fuel efficiency, operator comfort, and advanced hydraulic control. With an operating weight of approximately 19,000 kg and a net engine output of around 200 horsepower, the L120E was designed for demanding applications in quarrying, road construction, and bulk material handling.
Volvo CE, a division of the Swedish industrial giant Volvo Group, has long been known for its emphasis on safety, visibility, and operator ergonomics. The L120E featured a load-sensing hydraulic system, a spacious cab with low noise levels, and the optional CDC (Comfort Drive Control) system—a joystick-based steering alternative aimed at reducing operator fatigue during long shifts.
Terminology Annotation

• CDC (Comfort Drive Control): Volvo’s joystick steering system that replaces the traditional steering wheel, allowing fingertip control of loader direction.
  
• Load-Sensing Hydraulics: A system that adjusts hydraulic flow based on demand, improving fuel efficiency and responsiveness.
  
• Articulated Steering: A steering method where the front and rear frames pivot at a central joint, common in wheel loaders.
  
• Steering Valve Block: A hydraulic control unit that directs fluid to the steering cylinders based on operator input.
  

Symptoms of Steering Delay and Asymmetry
Operators using the CDC system on the L120E have occasionally reported steering inconsistencies, particularly when turning left. The symptoms include:

• Delayed response when initiating a left turn via the CDC joystick
  
• Sluggish articulation compared to right turns
  
• Intermittent normal operation, suggesting a non-mechanical fault
  
• No issues with other hydraulic functions such as lift or tilt
  

In one recycling yard in southern Sweden, an L120E exhibited slow left steering during cold mornings. After warming up, the issue would sometimes resolve, pointing to a temperature-sensitive hydraulic or electronic component.
Root Causes and Diagnostic Pathways
Steering irregularities in CDC-equipped L120E loaders can stem from several sources:
Hydraulic circuit imbalance:

• Uneven flow to left vs. right steering cylinders due to valve wear or contamination
  
• Internal leakage in one cylinder causing reduced articulation force
  
• Air trapped in the steering lines affecting responsiveness
  

Electronic control faults:

• CDC joystick signal degradation due to worn potentiometers or loose connectors
  
• Software calibration drift in the steering control module
  
• Faulty solenoid or proportional valve in the steering valve block
  

Mechanical linkage issues:

• Misalignment in the articulation joint
  
• Wear in the pivot bearings or bushings causing resistance
  

Recommended diagnostic steps:

• Swap hydraulic hoses at the valve block to test for joystick signal asymmetry
  
• Use a diagnostic tool to read CDC input values and compare left/right commands
  
• Pressure test steering cylinders during left and right articulation
  
• Inspect valve block for contamination and clean or replace solenoids as needed
  

In a fleet in Alberta, a technician resolved a similar issue by replacing a faulty proportional valve that was intermittently sticking during left turns. The valve’s internal spool had minor scoring, causing unpredictable flow restriction.
Repair Strategies and Component Recommendations
To restore consistent steering performance:

• Flush the hydraulic system and replace filters to eliminate contamination
  
• Replace or rebuild steering cylinders if internal leakage is confirmed
  
• Upgrade CDC joystick if signal degradation is detected
  
• Replace steering valve block solenoids and recalibrate control software
  

Suggested specs:

• Hydraulic system pressure: ~250 bar (3,625 psi)
  
• Steering cylinder stroke: ~400 mm
  
• CDC joystick voltage range: 0–5V analog signal
  
• Valve block solenoid resistance: ~10–15 ohms
  

In one retrofit project in Texas, a contractor replaced the CDC joystick with a newer model from the L120F series. After minor wiring adjustments and software updates, steering response improved significantly.
Preventive Measures and Operator Tips
To minimize steering issues in CDC-equipped loaders:

• Avoid aggressive joystick movements during cold starts
  
• Perform monthly calibration checks using Volvo’s diagnostic interface
  
• Keep hydraulic fluid clean and within recommended viscosity range
  
• Train operators to recognize early signs of steering lag or asymmetry
  

In a quarry in New Zealand, implementing a pre-shift CDC function test reduced steering-related downtime by 80% over six months.
Final Thoughts
The Volvo L120E remains a reliable and capable wheel loader, and the CDC system offers ergonomic advantages when functioning properly. Steering delays—especially directional asymmetry—can be traced to hydraulic imbalance, electronic signal faults, or valve wear. With structured diagnostics and quality component replacement, the machine’s precision and responsiveness can be fully restored.
In the subtle movement of a joystick and the smooth pivot of steel, the L120E proves that comfort and control are not luxuries—they’re the foundation of productivity.