Komatsu PC750LC-7 Fault Code E114: Complete Diagnostic Guide

What is Komatsu PC750LC-7 Fault Code E114?

Fault Code E114 on the Komatsu PC750LC-7 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 or detecting temperatures outside the normal operating parameters.

The ECM relies on accurate coolant temperature data to optimize fuel injection timing, engine protection protocols, and hydraulic system performance. On the PC750LC-7's SAA6D140E-3 engine, this sensor is critical for preventing overheating and maintaining the engine's operational efficiency. When E114 triggers, the ECM may default to fail-safe mode, significantly impacting machine productivity.

Common Symptoms

When Code E114 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel with possible audible alarm
• Engine derate or reduced power output as the ECM enters protective mode
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Hard starting conditions, especially in cold weather, due to incorrect fuel mapping
• Increased fuel consumption as the ECM compensates for missing temperature data

Potential Causes

The most common technical causes for E114 on used PC750LC-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal element breakdown
• Damaged wiring harness near the sensor connector, particularly where the harness routes along the engine block (known rub point)
• Corroded or loose connector pins at the sensor or ECM connection points
• ECM internal circuit failure (less common but possible in high-hour machines)
• Coolant contamination causing sensor element coating or deterioration
• Ground circuit issues affecting sensor signal return path

How to Troubleshoot and Fix Code E114

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block's coolant passage. Check for physical damage, coolant leaks, or corrosion. On used excavators, carefully examine the wiring harness for abrasion points where it contacts the engine or frame—this is a common failure point on the PC750LC-7.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 20°C (68°F), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness continuity from sensor connector to ECM and check for short circuits to ground.

Step 3: Signal Voltage Check With the sensor connected and ignition on (engine off), backprobe the sensor connector and verify the reference voltage from the ECM (typically 5 volts). If voltage is absent or incorrect, trace the circuit toward the ECM for breaks or shorts.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu sensor (Part #6732-81-3110 or equivalent). For used machines, always apply dielectric grease to connector pins to prevent future corrosion. Clear codes using Komatsu diagnostic software (KOMTRAX) and verify repair with a test run.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC750LC-7 service manual and consider professional technician assistance for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.