Komatsu PC750LC-7 Fault Code E116: Complete Diagnostic Guide

What is Komatsu PC750LC-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 or detecting temperatures outside the normal operating parameters for the SAA6D140E-3 engine.

This fault is critical for the PC750LC-7 because the ECM relies on accurate coolant temperature data to manage fuel injection timing, engine protection protocols, and hydraulic system performance. When E116 triggers, the engine may enter a protective derate mode to prevent overheating damage, significantly impacting productivity on job sites.

Common Symptoms

When Code E116 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel with possible audible alarm
• Reduced engine power or automatic derate limiting RPM and hydraulic flow
• Erratic temperature gauge readings showing unusually high or low coolant temperatures
• Hard starting conditions or rough idle, especially during cold starts
• Increased fuel consumption due to ECM operating in default "limp mode" parameters

Potential Causes

The most common technical causes for E116 on used PC750LC-7 excavators include:

• Failed coolant temperature sensor due to internal element degradation (common after 8,000+ operating hours)
• Corroded or loose connector pins at the sensor harness connection point near the thermostat housing
• Damaged wiring harness from rubbing against engine components or heat exposure along the routing path
• Low coolant level causing air pockets that prevent accurate temperature sensing
• ECM internal fault or corrupted calibration data (less common but possible in high-hour machines)
• Aftermarket sensor incompatibility if previous repairs used non-OEM parts

How to Troubleshoot and Fix Code E116

Step 1: Visual Inspection Begin by checking coolant level in the radiator and overflow tank. Inspect the coolant temperature sensor (located on the engine block near the thermostat) for physical damage, coolant leaks, or corrosion. On used excavators, carefully examine the wiring harness for chafing, especially where it contacts metal brackets or passes near hot exhaust components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult your service manual for exact specifications). Check for voltage supply at the harness connector—you should see approximately 5 volts reference voltage from the ECM.

Step 3: Connector and Harness Verification Inspect connector pins for corrosion, bent terminals, or moisture intrusion—common issues in machines operating in wet or dusty environments. Test continuity from the sensor connector back to the ECM pins to identify any open circuits or high-resistance connections.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu coolant temperature sensor (Part #6732-81-3210 or equivalent). After installation, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then monitor for code recurrence during a complete heat cycle.

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