Komatsu PC750-7 Fault Code E315: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E315?

Fault Code E315 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 (typically above 4.9V). The sensor, located on the engine block near the thermostat housing, provides critical temperature data to the ECM for fuel injection timing, cooling fan activation, and cold-start enrichment calculations.

On the PC750-7's SAA6D140E-3 engine, accurate coolant temperature readings are essential for maintaining optimal combustion efficiency and preventing thermal damage to critical components.

Common Symptoms

• Check Engine warning lamp illuminated on the monitor panel
• Engine may enter derate mode, limiting power output by 15-25%
• Cooling fans running continuously at maximum speed
• Erratic idle behavior, particularly during cold starts
• Inaccurate temperature gauge readings or gauge displaying maximum/minimum values

Potential Causes

• Coolant temperature sensor failure due to internal short or degradation
• Wiring harness damage from vibration, heat exposure, or rodent activity
• Corroded connector pins at the sensor or ECM interface
• Open circuit caused by broken wires near routing clamps
• ECM ground fault affecting sensor reference voltage
• Previous coolant leaks causing mineral deposits on sensor tip (common in high-hour machines)

How to Troubleshoot and Fix Code E315

Step 1: Visual Inspection Locate the coolant temperature sensor on the engine block. Inspect the wiring harness for chafing, particularly where it routes near exhaust components and hydraulic lines. On used PC750-7 units, check for previous repairs or splices that may have degraded over time. Examine connector pins for corrosion, green oxidation, or bent terminals.

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; at 80°C (176°F), approximately 300Ω. Verify the ECM provides 5V reference voltage at the harness connector with the key on.

Step 3: Circuit Continuity Check Test continuity between the sensor connector and ECM terminals using Komatsu VHMS diagnostic software or a multimeter. Resistance should be below 5Ω. Check for shorts to ground on both signal and reference wires.

Step 4: Component Replacement If sensor resistance is out of specification, replace with an OEM-equivalent unit. Apply dielectric grease to connector pins before reassembly. Clear codes using diagnostic equipment and verify repair with a test cycle.

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