Komatsu PC75UU-2: Troubleshooting Error Code EE and Starting Issues

[MikePhua]

The Komatsu PC75UU-2 is a reliable and compact mini-excavator, popular for its versatility and efficiency in construction, demolition, and landscaping applications. However, like any complex machine, it can encounter issues, particularly with its electronic system. One of the common problems reported by operators is the appearance of an Error Code EE on the machine’s diagnostic system, coupled with a failure to start. This guide aims to help you understand the causes of this issue, provide troubleshooting tips, and outline the steps for resolution.
Understanding the Komatsu PC75UU-2 and Its Electronic System
The Komatsu PC75UU-2 is a hydraulic mini-excavator that features a sophisticated electronic control system designed to manage various aspects of the machine's performance. From engine control to hydraulic operations, the machine uses sensors, relays, and control modules to maintain optimal functionality. The Error Code EE specifically points to a problem in the electrical or control system, often related to starting issues.
Common Causes for Error Code EE and Non-Starting
Error codes in the Komatsu PC75UU-2 serve as diagnostic tools that pinpoint the specific issue in the system. In this case, the Error Code EE typically indicates an issue with the engine start circuit, ignition system, or a malfunction in one of the key electronic components. Below are some of the most common reasons why this error code may appear and prevent the machine from starting.
1. Faulty Start Solenoid or Relay
One of the leading causes of starting issues in the PC75UU-2 is a malfunction in the start solenoid or start relay. The solenoid is responsible for engaging the starter motor when you attempt to start the engine, while the relay controls the flow of electrical current to the solenoid.

• Symptoms: If the solenoid or relay fails, the engine may fail to crank, even though the ignition switch appears to work. This can cause the machine to display the Error Code EE.
  
• Troubleshooting: Test the start solenoid and relay with a multimeter. A faulty solenoid or relay will need to be replaced to restore proper function.
  

2. Low or Faulty Battery
A weak or faulty battery can trigger the Error Code EE and prevent the machine from starting. The PC75UU-2 requires sufficient voltage to activate the electronic control system and start the engine.

• Symptoms: If the battery voltage is too low, the system may not send a start signal to the starter motor, resulting in a non-start condition and an error code.
  
• Troubleshooting: Check the battery voltage using a multimeter. If the voltage is low (below 12 volts), recharge the battery or replace it if necessary.
  

3. Faulty Ignition Switch
The ignition switch plays a pivotal role in the starting process of the PC75UU-2. If the switch malfunctions or fails, it may not send the correct signal to the control system, causing the Error Code EE and preventing the machine from starting.

• Symptoms: A faulty ignition switch will cause the engine to remain unresponsive when the key is turned to the "start" position.
  
• Troubleshooting: Inspect the ignition switch for any visible signs of damage or wear. Using a multimeter, check for continuity when the key is turned to the start position. If there is no continuity, replace the ignition switch.
  

4. Issues with the Engine Control Module (ECM)
The Engine Control Module (ECM) is the brain of the PC75UU-2’s electronic system. It monitors the engine’s performance and manages the starting process. If the ECM is malfunctioning or if there is a wiring issue, it may prevent the engine from starting and display an error code.

• Symptoms: The machine may not respond to the ignition, and the Error Code EE will persist. In some cases, the ECM may throw additional error codes related to engine management.
  
• Troubleshooting: Use an OBD scanner or diagnostic tool to check for additional error codes related to the ECM. If the ECM is faulty, it may need to be reprogrammed or replaced by a professional technician.
  

5. Poor Ground Connection or Wiring Issues
A poor ground connection or damaged wiring can disrupt the starting system in the PC75UU-2. This is particularly relevant in machines that have been in operation for a while or have been exposed to harsh conditions that could cause wear and tear on the wiring.

• Symptoms: Intermittent starting issues, failure to start, or error codes like EE can indicate wiring problems.
  
• Troubleshooting: Inspect the wiring and ground connections around the starter motor, ignition switch, and battery. Clean any corrosion on terminals, and check for loose or damaged wires. Repair or replace any faulty wiring.
  

6. Faulty Safety Interlocks
The Komatsu PC75UU-2, like most heavy equipment, is equipped with safety interlocks that prevent the engine from starting under certain conditions, such as when the machine is not in neutral or when the operator is not seated. If one of these interlocks malfunctions, it may prevent the machine from starting and trigger the Error Code EE.

• Symptoms: The machine will not start, and the error code may be displayed without any clear cause in the ignition or battery system.
  
• Troubleshooting: Check the operation of all safety interlocks, including the neutral safety switch and seat switch. Test for continuity in the circuits, and replace any malfunctioning interlocks.
  

Steps to Resolve the Error Code EE
If you encounter the Error Code EE on your Komatsu PC75UU-2 and the machine won’t start, follow these steps to diagnose and fix the problem:
Step 1: Check the Battery

• Measure the battery voltage using a multimeter. If the voltage is low, charge or replace the battery.
  
• Inspect the battery terminals for corrosion or loose connections and clean them as needed.
  

Step 2: Inspect the Ignition Switch and Solenoid

• Use a multimeter to check for continuity in the ignition switch and the start solenoid.
  
• If either component shows signs of failure, replace them.
  

Step 3: Examine the Engine Control Module (ECM)

• Use an OBD scanner to retrieve error codes from the ECM.
  
• If the ECM is faulty, it may require reprogramming or replacement by a Komatsu-certified technician.
  

Step 4: Inspect Wiring and Ground Connections

• Check all wiring related to the ignition system for damage or wear.
  
• Ensure that ground connections are secure and free of corrosion.
  

Step 5: Test Safety Interlocks

• Inspect the seat switch, neutral safety switch, and other interlocks to ensure they are functioning properly.
  
• Repair or replace any faulty switches or connections.
  

Preventative Maintenance to Avoid Starting Issues
To minimize the chances of encountering starting issues and Error Code EE on your Komatsu PC75UU-2, regular maintenance is essential:

• Check and maintain the battery: Regularly inspect the battery and charge it to ensure proper voltage.
  
• Inspect wiring and connections: Periodically check the wiring and ground connections for wear and corrosion.
  
• Lubricate and clean components: Ensure the ignition system and solenoids are free from debris and properly lubricated.
  
• Test safety interlocks: Periodically test the operation of safety features to ensure they are functioning as intended.
  

Case Studies of Error Code EE and Starting Issues
Case Study 1: Ignition Switch Failure
A Komatsu PC75UU-2 operator in California experienced an Error Code EE that prevented the machine from starting. After testing the battery and confirming it was functioning correctly, the technician discovered that the ignition switch was faulty. Replacing the ignition switch resolved the issue, and the machine was able to start normally.
Case Study 2: Battery Voltage Drop
In a construction project in Texas, a PC75UU-2 refused to start, displaying the Error Code EE. The operator had recently replaced the battery, but it turned out that the alternator was not charging it properly. After replacing the alternator, the error code was cleared, and the machine started without issues.
Conclusion
The Error Code EE on the Komatsu PC75UU-2 is often related to electrical system malfunctions, particularly issues with the start solenoid, battery, ignition switch, or wiring. By carefully diagnosing the problem and following the troubleshooting steps outlined above, you can quickly identify and resolve the issue, getting your mini-excavator back to work. Regular maintenance and careful attention to electrical components will help prevent future starting problems and ensure that your Komatsu PC75UU-2 continues to perform reliably on the job site.