Komatsu PC750-7 Fault Code E982: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E982?

Fault Code E982 on the Komatsu PC750-7 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormally high voltage signal or open circuit condition.

This diagnostic trouble code is generated by the Engine Control Module (ECM) when the coolant temperature sensor signal falls outside the manufacturer's specified parameters. The sensor, typically a negative temperature coefficient (NTC) thermistor, should produce voltage readings that correspond to actual coolant temperatures.

On the PC750-7's SAA6D140E-3 engine, accurate coolant temperature data is critical for proper fuel injection timing, cold-start enrichment, and cooling fan activation. An erroneous signal can lead to improper engine management decisions, potentially causing overheating or excessive fuel consumption.

Common Symptoms

• Check Engine light illuminated on the monitor panel
• Engine may enter derate mode, limiting power output
• Cooling fan running continuously or not engaging at all
• Erratic temperature gauge readings or gauge showing maximum/minimum values
• Poor cold-start performance and rough idle during warm-up
• Increased fuel consumption due to incorrect fuel mapping

Potential Causes

• Coolant temperature sensor failure due to age or thermal cycling
• Open circuit in the sensor wiring harness
• Corroded or damaged connector pins at the sensor or ECM
• Harness chafing against engine components (common near exhaust manifolds on high-hour machines)
• ECM ground circuit issues affecting sensor reference voltage
• Previous improper repairs or spliced wiring degradation

How to Troubleshoot and Fix Code E982

Step 1: Visual Inspection Locate the coolant temperature sensor on the engine block near the thermostat housing. Inspect the connector for corrosion, moisture intrusion, or damaged pins. On used excavators, carefully examine the harness routing for friction wear against brackets or heat shields—a common issue on machines exceeding 10,000 hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 20°C (68°F), expect approximately 2.5-3.0 kΩ. Check for 5V reference voltage at the harness connector with the key on. Verify continuity between the ECM and sensor connector pins.

Step 3: Component Replacement If sensor resistance is out of specification or the circuit tests confirm an open condition, replace the coolant temperature sensor with an OEM-equivalent part. Clear the fault code using Komatsu VHMS or compatible diagnostic software and verify proper operation.

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Disclaimer: This guide is for informational purposes only. Always consult qualified technicians and refer to official Komatsu service documentation for your specific machine serial number before performing repairs.