Komatsu PC750LC-7 Fault Code E202: Complete Diagnostic Guide

What is Komatsu PC750LC-7 Fault Code E202?

Fault Code E202 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 E202 triggers, the engine may enter a protective derate mode to prevent overheating damage, significantly impacting productivity on job sites.

Common Symptoms

When Code E202 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Reduced engine power or automatic derate limiting maximum RPM to approximately 1,500-1,800 RPM
• Erratic temperature gauge readings that fluctuate abnormally or show unrealistic values
• Difficulty starting in cold conditions if the ECM receives faulty cold-start temperature data
• Increased fuel consumption due to improper fuel mapping based on incorrect temperature readings

Potential Causes

The most common technical causes for E202 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, particularly where the harness routes along the cylinder head
• Contaminated coolant causing sensor element fouling or scaling
• ECM internal fault (rare, but possible in high-hour machines with electrical system stress)
• Poor ground connection at the sensor circuit ground point

How to Troubleshoot and Fix Code E202

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block near the thermostat housing. Check for coolant leaks, corrosion on the connector, and physical damage to the wiring harness. On used excavators, pay special attention to harness wear points where cables contact metal surfaces.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 68°F (20°C), resistance should read approximately 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 reference voltage from the ECM.

Step 3: Connector and Ground Verification Clean all connector pins with electrical contact cleaner and inspect for bent pins or corrosion. Verify the ground circuit continuity between the sensor ground and chassis ground (should read less than 1 ohm resistance).

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu coolant temperature sensor (Part #6732-81-3210 or equivalent). For used machines, always replace the connector pigtail if corrosion is present to prevent recurring faults.

Step 5: Clear Code and Verify Use Komatsu diagnostic software (KOMTRAX) or a compatible scan tool to clear the fault code. Run the engine through a complete warm-up cycle and monitor for code recurrence.

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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 from certified Komatsu technicians for complex electrical diagnostics.