Komatsu PC750SE-7 Fault Code E113: Complete Diagnostic Guide

What is Komatsu PC750SE-7 Fault Code E113?

Fault Code E113 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 fan operation. When this sensor fails or sends erratic signals, the ECM cannot properly regulate engine temperature, potentially leading to overheating, reduced performance, or engine protection mode activation.

Common Symptoms

When Code E113 is active on your PC750SE-7, operators typically experience:

• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Engine derate mode where power output is significantly reduced to prevent damage
• Cooling fan running continuously at high speed, even when engine temperature appears normal
• Rough idle or difficulty starting, especially in cold conditions
• Inaccurate temperature gauge readings showing extreme high or low temperatures that don't match actual conditions

Potential Causes

The most common technical reasons for E113 on used PC750SE-7 excavators include:

• Coolant temperature sensor failure due to age, thermal cycling, or internal resistance drift
• Damaged or corroded wiring harness at connector points, particularly where the harness routes near the engine block
• Corroded sensor connector pins from coolant leaks or moisture intrusion
• Broken or chafed wires at known rub points near the turbocharger or exhaust manifold
• ECM internal fault (less common) affecting the sensor input circuit
• Poor ground connections at the sensor or ECM mounting points

How to Troubleshoot and Fix Code E113

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block (typically near the thermostat housing). Check for coolant leaks, corrosion on the connector, and physical damage. On used excavators, carefully examine the wiring harness for chafing, especially where it contacts hot engine components or sharp edges.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness voltage with the key on, engine off—you should see approximately 5 volts at the sensor connector from the ECM.

Step 3: Circuit Verification Check for continuity between the sensor connector and ECM pins. Inspect for short circuits to ground or power. Clean all connector pins with electrical contact cleaner and apply dielectric grease to prevent future corrosion.

Step 4: Component Replacement If the sensor tests outside specifications or the harness shows damage, replace the faulty component. For used machines, always replace the connector pigtail if corrosion is present, as this prevents recurring failures. Clear the code using Komatsu diagnostic software (KOMTRAX or equivalent) and perform a test run.

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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.