Troubleshooting the Hitachi EX 120-3 PVC Computer System

[MikePhua]

The Hitachi EX 120-3, a part of the Hitachi EX series of hydraulic excavators, is a popular and reliable machine in the construction and mining industries. Known for its powerful engine and advanced hydraulic system, this excavator is designed to handle heavy-duty tasks such as digging, lifting, and moving large materials. However, like all machines, the EX 120-3 is not immune to technical issues, particularly with its computer system, such as the PVC (Programmable Value Controller) that helps manage various functions.
This article delves into common issues with the PVC computer system in the Hitachi EX 120-3 and provides guidance on troubleshooting and resolving these problems. Understanding how the PVC system works, how to diagnose errors, and the best solutions will help keep the machine running efficiently.
What is the PVC System in the Hitachi EX 120-3?
The PVC (Programmable Value Controller) is an integral part of the control system in the Hitachi EX 120-3 excavator. It’s a computer-based unit that manages and regulates various machine parameters, including engine speed, hydraulic performance, and fuel efficiency. The PVC system communicates with sensors throughout the excavator to ensure optimal performance by adjusting values in real-time based on operational conditions.
The PVC system is crucial for controlling functions such as:

• Hydraulic Flow: The system manages the hydraulic pumps, ensuring that the correct amount of fluid is pumped to the arms, bucket, and boom.
  
• Engine Control: It controls the engine speed and fuel delivery for efficient operation.
  
• Safety Features: The PVC system can detect faults in the machine’s performance, including low hydraulic pressure or electrical issues, and can trigger warning lights or alarms.
  

The system relies on sensors, wiring, and connections throughout the machine, and any failure or malfunction in these components can lead to issues with the machine’s performance.
Common Issues with the PVC System in the Hitachi EX 120-3
There are a variety of issues that can arise with the PVC system. Below are some of the most common problems encountered by operators:
1. PVC System Error Codes
One of the most frequent issues is the appearance of error codes on the machine's display, indicating a malfunction in the PVC system. These error codes often point to specific problems, such as a faulty sensor or wiring issue.

• Example Codes: Error codes such as “E01,” “E03,” or “E06” are commonly seen in the EX 120-3. These codes generally refer to issues with sensors or control systems related to the hydraulic pumps or engine management.
  
• Possible Causes:
  • Loose or damaged wiring connections.
    
  • Faulty sensors providing incorrect data to the PVC system.
    
  • Problems with the ECU (Electronic Control Unit) itself.
    

2. Poor Hydraulic Performance
When the PVC system is malfunctioning, it can lead to poor hydraulic performance, which manifests as sluggish or unresponsive boom and arm movements. If the system detects a problem, it might reduce the hydraulic pressure to prevent further damage to the machine.

• Symptoms: Slow or jerky movements, inability to lift heavy loads, or inconsistent arm and bucket control.
  
• Possible Causes:
  • Faulty sensors or connectors affecting hydraulic pressure readings.
    
  • Incorrect hydraulic fluid levels or fluid contamination.
    
  • Wiring issues in the PVC system that prevent proper communication between the ECU and hydraulic pumps.
    

3. Engine Speed and Fuel Efficiency Issues
The PVC system also plays a key role in controlling the engine speed and fuel delivery. If there’s an issue with the system, the engine might experience irregular speed fluctuations or poor fuel efficiency.

• Symptoms: Engine speed may fluctuate unexpectedly, or the engine may idle too high or too low, causing increased fuel consumption.
  
• Possible Causes:
  • Faulty sensors providing inaccurate engine data.
    
  • Problems with the ECU or wiring between the PVC and engine management system.
    
  • Issues with the fuel system, such as clogged filters or injectors.
    

4. Warning Lights or Alarms
When the PVC system detects an issue, it may trigger warning lights or alarms on the machine’s dashboard to alert the operator to a potential malfunction. These warnings are designed to prevent further damage by notifying the operator to check specific systems.

• Symptoms: Warning lights for hydraulic pressure, engine performance, or overall system malfunction.
  
• Possible Causes:
  • A sensor failure or disconnection.
    
  • Electrical issues within the PVC or control system.
    
  • Low fluid levels or inadequate maintenance on the hydraulic system.
    

How to Diagnose PVC System Problems in the Hitachi EX 120-3
Diagnosing issues with the PVC system can be complex, but following a systematic approach can help isolate the problem.
Step 1: Check the Error Codes
Start by reading the machine’s error codes through the onboard diagnostic system. These codes will point you toward the faulty components or system issues that need attention. Use the service manual or diagnostic tool to interpret the codes.
Step 2: Inspect Wiring and Connections
The PVC system relies on numerous wiring connections between sensors, the ECU, and the hydraulic components. Inspect the wiring for any loose connections, corrosion, or physical damage. Pay close attention to connections that are exposed to harsh environmental conditions, as these can wear out more quickly.
Step 3: Test the Sensors
Each sensor in the system sends data to the PVC system. Test the sensors for proper function using a multimeter or diagnostic tool. If a sensor is sending faulty readings, it may need to be replaced.
Step 4: Inspect the Hydraulic System
Ensure that the hydraulic system is operating correctly. Check the hydraulic fluid levels and inspect for leaks or contamination. Clean filters and replace fluids as necessary. Hydraulic performance issues can often be traced back to problems in this area.
Step 5: Consult the Manual or a Technician
If the error persists or is difficult to diagnose, refer to the machine’s service manual for more detailed troubleshooting steps. If necessary, consult a certified technician who has experience with the Hitachi EX series and its computer systems.
Solutions for PVC System Issues
If troubleshooting reveals a fault in the PVC system, the following steps can help resolve the issue:

• Replace Faulty Sensors: If a sensor is malfunctioning, replacing it is often the best solution. Be sure to use OEM parts to ensure compatibility with the system.
  
• Repair or Replace Wiring: If wiring issues are detected, repair any damaged connections and ensure proper insulation to prevent future issues.
  
• Check and Replace Hydraulic Fluids: Ensure that hydraulic fluids are clean and at the correct levels. Contaminated or low fluid levels can cause significant issues with performance.
  
• ECU Replacement: If the ECU is malfunctioning, replacing the unit may be necessary. This is a more expensive solution but is sometimes required for complex electrical problems.
  

Preventive Measures for the PVC System
Regular maintenance can prevent many issues with the PVC system. Here are some preventive steps:

1. Routine Inspections: Regularly inspect the wiring, sensors, and hydraulic system for signs of wear or damage.
   
2. Use OEM Parts: Always use original equipment manufacturer (OEM) parts when replacing sensors, wiring, or other components. OEM parts are designed to be compatible with the machine's systems.
   
3. Maintain Hydraulic Fluids: Regularly change hydraulic fluids and replace filters to ensure smooth operation and prevent clogging or contamination.
   
4. System Calibration: Periodically calibrate the PVC system to ensure optimal performance.
   

Conclusion
The Hitachi EX 120-3 is a highly capable machine, and its PVC system plays a crucial role in ensuring its smooth operation. Understanding how the system works and knowing how to troubleshoot and maintain it can help prevent costly repairs and downtime. Regular inspections, proper maintenance, and timely repairs will keep your machine running efficiently, ensuring long-lasting performance in tough work environments. By taking a proactive approach to the PVC system, operators can avoid common issues and keep their equipment operating at its best.