What is Komatsu PC450-7 Fault Code E-15?

Fault Code E-15 on the Komatsu PC450-7 excavator 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 signals that the ECM is receiving either an out-of-range voltage signal from the coolant temperature sensor or detecting an open/short circuit in the sensor's wiring harness.

The coolant temperature sensor plays a critical role in the PC450-7's performance management. It provides real-time data that the ECM uses to adjust fuel injection timing, idle speed, and cooling fan operation. When this sensor fails or sends incorrect data, the engine cannot optimize combustion or prevent overheating, potentially leading to severe engine damage or catastrophic failure in heavy-duty applications.

Common Symptoms

When Code E-15 is active on your Komatsu PC450-7, operators typically experience:

• Engine warning light illuminated on the dashboard (amber or red depending on severity)
• Engine running in derate mode with reduced power output to prevent overheating damage
• Cooling fan running continuously at maximum speed, even during cold starts
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Difficulty starting the engine in cold weather conditions due to improper fuel delivery calculations

Potential Causes

Based on field experience with used PC450-7 excavators, the most common causes of Code E-15 include:

• Faulty coolant temperature sensor (thermal element degradation common after 8,000+ operating hours)
• Corroded or damaged wiring connectors at the sensor junction near the thermostat housing—a known rub point on this model
• Harness chafing against the engine block during vibration, causing intermittent shorts to ground
• Coolant contamination causing sensor tip corrosion or buildup (especially in machines with neglected maintenance history)
• ECM internal fault (rare, but documented in PC450-7 units manufactured between 2004-2006)
• Low coolant levels causing sensor exposure to air rather than coolant

How to Troubleshoot and Fix Code E-15

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the cylinder head near the thermostat housing. Check the wiring harness for visible damage, abraded insulation, or corrosion at the connector. On used excavators, pay special attention to the harness routing—the PC450-7 has a known issue with harness contact against the alternator bracket.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms. Test the harness for continuity to the ECM (Pin 37 on the C2 connector) and check for shorts to ground. Voltage supply from the ECM should measure 5 volts with the key on.

Step 3: Sensor Replacement and Verification If resistance values are out of specification or the harness shows damage, replace the sensor with a genuine Komatsu part (PN: 6754-61-6210) and repair any damaged wiring. After replacement, clear the fault code using Komatsu diagnostic software (KOMTRAX Plus) or a compatible scan tool, then monitor the system during a complete heat cycle from cold start to operating temperature.

Critical Note for Used Equipment: Before replacing components, verify actual coolant temperature with an infrared thermometer compared to sensor readings. Many unnecessary sensor replacements occur due to overlooked harness issues or poor connector contact from years of thermal cycling.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC450-7 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or create safety hazards.