Komatsu PC450LC-6 Fault Code E231: Complete Diagnostic Guide

What is Komatsu PC450LC-6 Fault Code E231?

Fault Code E231 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Engine Control Module (ECM). This code specifically relates to the coolant temperature sensor sending irregular voltage signals outside the manufacturer's specified parameters to the ECM.

In the Komatsu PC450LC-6, the coolant temperature sensor plays a critical role in engine management, controlling fuel injection timing, idle speed, and engine protection protocols. When this sensor fails or provides inaccurate data, the ECM cannot properly regulate engine performance, potentially leading to overheating, poor fuel economy, or engine damage. This is particularly critical in high-hour used machines where sensor degradation is common.

Common Symptoms

When Code E231 is active, operators typically experience:

• Engine warning light illuminated on the instrument panel, often accompanied by an audible alarm
• Hard starting or rough idle, especially during cold starts when the ECM relies heavily on temperature data
• Engine derate mode activation, limiting power output to protect the engine from potential thermal damage
• Inaccurate temperature gauge readings showing extreme high or low temperatures that don't match actual operating conditions
• Increased fuel consumption due to improper fuel mapping based on faulty temperature signals

Potential Causes

The most common technical causes for E231 in used PC450LC-6 excavators include:

• Coolant temperature sensor failure due to age, thermal cycling, or internal resistance drift (common after 8,000+ operating hours)
• Damaged or corroded wiring harness at connector points, particularly where the harness routes near the engine block and experiences heat exposure
• Corroded or loose electrical connectors at the sensor or ECM connection points, especially in machines exposed to harsh environments
• Shorted or open circuits in the sensor wiring, often caused by harness chafing against engine components
• ECM internal fault (rare, but possible in high-hour machines with previous electrical issues)
• Coolant contamination causing sensor element coating or degradation

How to Troubleshoot and Fix Code E231

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block (typically near the thermostat housing). Check for physical damage, coolant leaks, or corrosion. Examine the wiring harness from sensor to ECM for signs of chafing, burns, or damage—pay special attention to areas where the harness contacts hot engine surfaces, a common wear point in used excavators.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures. At 20°C (68°F), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Test harness continuity from the sensor connector to the ECM, checking for opens or shorts to ground. Verify supply voltage from the ECM (typically 5V reference).

Step 3: Component Replacement and Verification If resistance values are out of specification or the sensor shows physical deterioration, replace the coolant temperature sensor with a genuine Komatsu part. Before installation, clean the sensor mounting location and apply appropriate thread sealant. For used machines, always inspect and clean connector terminals with electrical contact cleaner, as corrosion often causes intermittent faults. After replacement, clear codes using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, and perform a test run to verify repair.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number. If you're uncomfortable performing electrical diagnostics, consult a certified Komatsu technician to prevent further damage to your equipment.