What is Komatsu PC210LC-10 Fault Code E-20?

Fault Code E-20 on the Komatsu PC210LC-10 indicates a malfunction in the engine controller (ECM) communication system, specifically a CAN communication error between the engine ECM and the machine controller. This code signals that critical data exchange between the power management system and hydraulic control systems has been interrupted or degraded.

The CAN (Controller Area Network) bus is the nervous system of modern excavators, allowing the engine ECM, pump controller, and monitor panel to share real-time operational data. When communication fails, the PC210LC-10 cannot properly coordinate engine output with hydraulic demand, directly impacting fuel efficiency, power delivery, and diagnostic capabilities. This is particularly critical on the -10 series machines, which rely heavily on integrated electronic control for their advanced hydraulic matching system.

Common Symptoms

• Warning light illuminated on the monitor panel with "E-20" displayed, often accompanied by a buzzer alert
• Reduced engine power or inability to reach maximum RPM, as the ECM enters a protective derate mode
• Erratic hydraulic response, including inconsistent swing speed or sluggish boom/arm movements due to pump control communication loss
• Intermittent gauge failures on the monitor display, with engine temperature, fuel level, or hour meter readings dropping out
• Difficulty starting or extended cranking times as the controllers attempt to re-establish communication protocol

Potential Causes

The most frequent causes of E-20 on used PC210LC-10 excavators include:

• Corroded or loose CAN bus connectors at the ECM, particularly the 38-pin main harness connector known to accumulate moisture in machines operating in wet conditions
• Chafed wiring harness between the engine bay and cab, especially where the harness passes through the bulkhead near the hydraulic tank (common rub point on this model)
• Failed termination resistor on the CAN network, typically located inside the monitor panel or ECM housing
• ECM internal failure or corrupted software, more common in machines with 8,000+ operating hours
• Voltage fluctuations from a failing alternator or weak batteries (CAN systems require stable 24V supply)
• Water intrusion into the engine harness connectors from damaged cable glands or failed seals

How to Troubleshoot and Fix Code E-20

Step 1: Visual Inspection and Connector Check Begin by inspecting all CAN bus connectors at the engine ECM (mounted on the right side of the engine) and the machine controller under the operator's seat. Look for green corrosion, bent pins, or moisture. On used excavators, this is the most common culprit. Clean connectors with electrical contact cleaner and apply dielectric grease. Check the harness routing for chafe marks at the bulkhead pass-through and zip-tie any loose sections away from moving components.

Step 2: Electrical Testing with Diagnostic Tools Using a digital multimeter, check for proper voltage at the ECM power supply (should read 24V ±1V). Next, measure CAN-High and CAN-Low resistance between pins at the ECM connector (typically pins 22 and 23 on the 38-pin connector). With the key off and all controllers disconnected, you should read approximately 60 ohms, indicating proper termination resistors. Connect Komatsu KOMTRAX diagnostic software or a compatible diagnostic tool to read live CAN bus traffic and identify which controller is dropping communication.

Step 3: Component Replacement and Software Verification If connectors and wiring pass inspection, test the termination resistors (usually 120-ohm resistors at each end of the network). Replace any failed resistors before considering ECM replacement. For machines with 6,000+ hours, inspect the alternator output under load—CAN communication errors often correlate with voltage drops during high hydraulic demand. If all electrical checks pass, the ECM may require software reflashing or replacement. Always clear codes after repairs and perform a full operational test, monitoring for code recurrence during combined hydraulic functions.

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Disclaimer: This guide provides general troubleshooting information for the Komatsu PC210LC-10. Always consult the official Komatsu service manual for your machine's specific serial number range and consider engaging a certified Komatsu technician for complex electrical diagnostics. Improper repairs to CAN bus systems can cause cascading controller failures.