Komatsu PC750-7 Fault Code E980: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E980?

Fault Code E980 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 returns voltage readings outside the manufacturer's specified parameters (typically above 4.9V). The sensor, located on the engine block near the thermostat housing, provides critical temperature data that influences fuel injection timing, cooling fan activation, and cold-start enrichment strategies.

On the PC750-7's SAA6D140E-3 engine, accurate coolant temperature monitoring is essential for preventing thermal damage and maintaining optimal combustion efficiency. Ignoring this code can lead to engine overheating, increased fuel consumption, and accelerated component wear.

Common Symptoms

• Check Engine warning lamp illuminated on the monitor panel
• Engine may enter derate mode, limiting power output and hydraulic performance
• Cooling fans running continuously at maximum speed regardless of actual temperature
• Erratic idle behavior, particularly during cold starts
• Temperature gauge displaying maximum or minimum readings inconsistently

Potential Causes

• Coolant temperature sensor failure due to age or thermal cycling
• Wiring harness damage from vibration, abrasion against frame components, or rodent intrusion
• Corroded or contaminated connector pins at the sensor or ECM
• Open circuit in the signal wire between sensor and ECM
• ECM internal fault (rare but possible on high-hour machines)
• Previous improper repairs or spliced wiring from past owners

How to Troubleshoot and Fix Code E980

Step 1: Visual Inspection Locate the coolant temperature sensor on the engine block. Inspect the wiring harness for chafing, especially where it routes near hot exhaust components or sharp frame edges. On used PC750-7 units, check for corrosion on connector terminals—a common issue in machines exposed to harsh environments.

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

Step 3: Component Replacement If sensor resistance is out of specification or the circuit tests reveal faults, replace the coolant temperature sensor with a genuine Komatsu part. Clear the fault code using Komatsu VHMS or compatible diagnostic software, then verify repair by monitoring live data during a warm-up cycle.

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Disclaimer: This guide is for informational purposes only. Always consult qualified heavy diesel technicians and refer to official Komatsu service manuals before performing repairs.