What is Kobelco SK140LC-8 Fault Code 20051?

Fault Code 20051 on the Kobelco SK140LC-8 excavator indicates a communication error or malfunction within the machine's controller area network (CAN) system, specifically related to the transmission of data between the engine control module (ECM) and the main controller.

This diagnostic trouble code (DTC) appears when the CAN bus communication fails to maintain proper signal integrity between critical control modules. The Kobelco SK140LC-8 relies on continuous, real-time communication between its ECM, hydraulic controllers, and monitoring systems to optimize fuel efficiency, hydraulic response, and emission controls. When Code 20051 triggers, the machine's ability to coordinate these systems becomes compromised, potentially leading to performance degradation or protective derate modes.

This fault is particularly critical because it affects the backbone communication network that controls everything from engine parameters to hydraulic functions, making proper diagnosis essential for maintaining operational efficiency in used equipment.

Common Symptoms

• Warning lights illuminated on the instrument cluster, specifically the engine or system malfunction indicator
• Reduced engine power or automatic derate mode, limiting maximum RPM to protect the engine
• Erratic hydraulic response or sluggish operation during combined functions (swing and boom movement)
• Intermittent gauge failures where digital displays freeze, flicker, or show incorrect readings
• Difficulty starting or unexpected shutdowns during operation, especially under heavy loads

Potential Causes

The most common technical causes for Code 20051 on used SK140LC-8 excavators include:

• Corroded or damaged CAN bus connectors, particularly at junction points in the engine compartment where moisture accumulation occurs
• Wiring harness damage from chafing against the engine block or frame rails—a known wear point near the fuel filter housing on this model
• Faulty ECM or main controller, often due to voltage spikes from starter motor or alternator issues in aging electrical systems
• Poor ground connections at chassis grounding points, which degrade over time from corrosion
• Damaged terminating resistors within the CAN network, causing signal reflection and communication errors
• Aftermarket component interference, especially non-OEM monitoring systems or poorly installed accessories that tap into the CAN network

How to Troubleshoot and Fix Code 20051

Step 1: Visual Inspection of CAN Bus Harness Begin by tracing the CAN bus wiring harness from the ECM (located near the battery box) to the main controller. Look for obvious physical damage, particularly where harnesses pass through bulkheads or contact moving parts. On used excavators, check rubber grommets for deterioration that allows harness movement and eventual wire breakage.

Step 2: Connector and Ground Verification Disconnect and inspect all CAN bus connectors for corrosion, bent pins, or moisture intrusion. Use electrical contact cleaner and verify pins are making solid contact. Test all chassis ground points with a multimeter—resistance to battery negative should be less than 0.5 ohms. Clean and retighten ground connections as needed.

Step 3: CAN Bus Signal Testing Using a digital multimeter set to DC voltage, backprobe the CAN-High and CAN-Low wires at the ECM connector (typically yellow and green wires). With ignition on, you should measure approximately 2.5V on each line at rest. The voltage difference between CAN-High and CAN-Low during communication should fluctuate between 1.5-3.5V. No voltage or static readings indicate circuit failure.

Step 4: Terminating Resistor Check Measure resistance between CAN-High and CAN-Low terminals with all controllers disconnected. You should read approximately 60 ohms, indicating both 120-ohm terminating resistors are present. Incorrect readings suggest resistor failure—a common issue in machines over 5,000 hours.

Step 5: Advanced Diagnostics If previous steps don't resolve the issue, connect Kobelco SENS diagnostic software (or compatible aftermarket scanner) to read real-time CAN bus traffic and pinpoint which module is failing to communicate. This software can identify intermittent failures that don't show during static testing.

For used excavators, always check for evidence of previous electrical repairs—improper splicing or non-spec wire can cause intermittent communication failures that only appear under vibration or temperature extremes.

Disclaimer: This guide provides general troubleshooting information. Complex electrical diagnostics should be performed by qualified technicians with appropriate Kobelco service manuals and diagnostic equipment. Improper electrical work can cause additional system damage or safety hazards.