Komatsu PC750SE-7 Fault Code E116: Complete Diagnostic Guide

What is Komatsu PC750SE-7 Fault Code E116?

Fault Code E116 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 PC750SE-7, the coolant temperature sensor plays a critical role in engine management, controlling fuel injection timing, idle speed, and triggering cooling system responses. When this sensor fails or sends erratic signals, the ECM cannot properly regulate engine temperature, potentially leading to overheating, poor fuel economy, or engine protection mode activation.

Common Symptoms

When Code E116 is active on your PC750SE-7, operators typically experience:

• Warning light illumination on the instrument cluster, specifically the engine temperature or malfunction indicator
• Engine derate mode where power output is significantly reduced to prevent thermal damage
• Erratic temperature gauge readings that fluctuate abnormally or show maximum temperature immediately at startup
• Hard starting or rough idle, particularly in cold weather conditions
• Cooling fan running continuously at maximum speed regardless of actual engine temperature

Potential Causes

The most common technical causes for E116 on used PC750SE-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal element breakdown
• Wiring harness damage at known rub points near the engine block or cylinder head where vibration causes insulation wear
• Corroded or loose connector pins at the sensor plug, especially on machines operating in harsh environments
• ECM internal circuit issues affecting the sensor signal processing (less common)
• Coolant contamination causing sensor element coating or deterioration
• Ground circuit problems creating voltage reference issues

How to Troubleshoot and Fix Code E116

Step 1: Visual Inspection Begin by locating the coolant temperature sensor (typically mounted on the engine block or thermostat housing). Inspect the wiring harness for obvious damage, chafing, or burns. On used excavators, pay special attention to areas where the harness contacts metal surfaces or moving components. Check the connector for corrosion, bent pins, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures (consult Komatsu specifications, typically 2,000-3,000 ohms at 20°C). Test the harness continuity from the sensor connector back to the ECM. Check for voltage supply (usually 5V reference) from the ECM with the key on, engine off.

Step 3: Component Replacement and Verification If resistance values are out of specification or the sensor shows physical damage, replace it with a genuine Komatsu part to ensure proper calibration. After replacement, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool. Perform a test run and monitor coolant temperature readings to confirm proper operation.

Critical Note for Used Equipment: Before replacing the sensor, thoroughly clean all electrical connectors with contact cleaner and apply dielectric grease. Many E116 codes on older machines resolve with connector maintenance alone, saving unnecessary parts replacement costs.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional assistance for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.