Komatsu PC750LC-7 Fault Code E218: Complete Diagnostic Guide

What is Komatsu PC750LC-7 Fault Code E218?

Fault Code E218 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 E218 triggers, the engine may enter a protective derate mode to prevent overheating damage, significantly impacting productivity on job sites.

Common Symptoms

When Code E218 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel with reduced engine power
• Automatic engine derate limiting RPM to 1,200-1,500 range to protect components
• Erratic temperature gauge readings or gauge stuck at maximum/minimum positions
• Delayed hydraulic response due to reduced engine performance
• Difficulty starting in cold conditions if the ECM receives false low-temperature signals

Potential Causes

The most common technical causes for E218 on used PC750LC-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal short circuits
• Damaged wiring harness near the engine block where vibration causes wire chafing (common failure point behind the fuel filter assembly)
• Corroded or loose connector pins at the sensor plug, especially on machines operating in wet or coastal environments
• ECM internal fault affecting the temperature sensor circuit (less common but possible on high-hour machines)
• Actual engine overheating triggering legitimate high-temperature warnings alongside sensor issues

How to Troubleshoot and Fix Code E218

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 around the sensor base, and examine the wiring harness for abrasion, particularly where it routes near moving components or sharp edges.

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). Also 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 For used excavators, thoroughly inspect connector pins for corrosion or bent terminals. Clean contacts with electrical contact cleaner and apply dielectric grease. Perform a continuity test on the harness between the sensor and ECM connector to identify any breaks 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 replacement, clear codes using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool and verify proper operation.

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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.