What is Kobelco Fault Code U110A?

Fault Code U110A indicates a CAN communication error between the engine ECU and the main controller in Kobelco excavators. This diagnostic trouble code (DTC) specifically signals that the Controller Area Network (CAN) bus system has detected a loss of communication or irregular data transmission between critical control modules.

The CAN bus serves as the central nervous system of modern Kobelco excavators, allowing the Engine Control Module (ECM), hydraulic controller, and instrument cluster to share real-time operational data. When U110A triggers, it means the engine ECU is either not responding to requests from the main controller or is sending corrupted data packets. This disruption compromises the machine's ability to coordinate engine performance with hydraulic demands, potentially affecting productivity and fuel efficiency. For used excavators, this code often points to age-related deterioration in the electrical system rather than catastrophic component failure.

Common Symptoms

Operators typically experience these warning signs when U110A is active:

• Engine warning lamp illuminated on the instrument panel, often accompanied by a CAN communication error message on the display
• Intermittent loss of throttle response or engine not matching hydraulic load demands
• Erratic gauge readings including tachometer fluctuations or fuel level inconsistencies
• Reduced engine power or activation of derate mode limiting maximum RPM to protect the engine
• Hydraulic system delays as the controller cannot properly synchronize engine output with pump requirements

Potential Causes

The most common technical failures triggering U110A in used Kobelco excavators include:

• Corroded or damaged CAN bus connectors at the engine ECU or main controller harness connections—particularly vulnerable on machines operating in wet or corrosive environments
• Broken or frayed CAN communication wires (typically a twisted pair with 120-ohm termination resistance) due to harness rubbing against frame components near the engine bay
• Failing engine ECU with degraded internal communication circuits, common in excavators exceeding 8,000 operating hours
• Low battery voltage or poor grounding causing insufficient power supply to maintain stable CAN bus voltage (should be 2.5V nominal on each wire)
• Water intrusion into sealed connectors, especially at known vulnerable points like the engine firewall pass-through

How to Troubleshoot and Fix Code U110A

Step 1: Perform Visual Inspection Begin by examining all wiring harnesses between the engine compartment and cab. Focus on areas where harnesses contact metal surfaces or moving parts. Check the main controller connector (typically located under the operator seat or behind the display panel) and the engine ECU connector for corrosion, bent pins, or moisture. On used excavators, pay special attention to connector seals—deteriorated rubber boots allow water penetration that causes intermittent communication failures.

Step 2: Test CAN Bus Integrity Using a digital multimeter, measure resistance between the two CAN High and CAN Low wires at the engine ECU connector with the ignition off and harness disconnected. You should read approximately 60 ohms (two 120-ohm terminating resistors in parallel). Deviation from this value indicates open circuits, shorts, or termination resistor failure. Next, check voltage levels with ignition on: both CAN wires should show approximately 2.5V DC relative to chassis ground, fluctuating slightly during communication.

Step 3: Verify Power Supply and Grounds Measure battery voltage at the engine ECU power supply pin—it must be at least 12.5V with the engine off and 13.8-14.4V during operation. Check the ECU ground circuit for resistance to chassis ground (should be less than 0.5 ohms). Corroded ground studs are extremely common on used machines and cause numerous phantom communication errors.

Step 4: Advanced Diagnostics If basic checks pass, connect Kobelco diagnostic software (or compatible scan tool supporting J1939 protocol) to monitor live CAN bus traffic. Watch for message timeout errors or checksum failures that indicate which module is failing to communicate properly. Clear codes and observe if U110A returns immediately or only under specific conditions (vibration, temperature changes), which suggests intermittent harness faults.

Step 5: Component Replacement Replace damaged connectors or harness sections rather than attempting repairs with electrical tape—proper sealed automotive connectors are essential. If the engine ECU is confirmed faulty through substitution testing or professional diagnosis, ensure replacement units match the machine's software calibration to avoid compatibility issues.

Disclaimer: This guide provides general troubleshooting information for experienced technicians. CAN bus diagnostics require specialized knowledge and equipment. Always consult Kobelco service manuals for model-specific procedures, and consider professional diagnosis for used excavators where multiple electrical issues may coexist.