What is Komatsu PC220-7 Fault Code E315?

Komatsu PC220-7 fault code E315 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 to the ECM, preventing accurate monitoring of engine operating temperature.

The coolant temperature sensor plays a critical role in the PC220-7's SAA6D102E-2 engine management system. It directly affects fuel injection timing, idle speed control, and engine protection protocols. When the ECM cannot reliably read engine temperature, it may force the machine into a derate mode to prevent potential overheating damage, significantly impacting productivity on the jobsite.

Common Symptoms

• Warning light illuminated on the instrument panel, often accompanied by an audible alarm
• Engine running in high idle continuously, regardless of load conditions
• Reduced engine power or activation of power derate mode to protect components
• Black smoke from the exhaust due to improper fuel mixture compensation
• Difficulty starting when the engine is cold, or abnormal warm-up behavior

Potential Causes

The E315 code on used PC220-7 excavators typically stems from age-related component degradation. The coolant temperature sensor itself commonly fails after years of thermal cycling. Wiring harness damage is frequent near the thermostat housing where vibration and heat cause insulation breakdown and exposed copper strands.

Connector corrosion at the sensor plug is especially common in machines operating in wet or coastal environments. The ECM may also misread sensor values if ground connections have deteriorated. On higher-hour machines, coolant contamination can coat the sensor tip, causing inaccurate readings without actual electrical failure.

How to Troubleshoot and Fix Code E315

Step 1: Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to verify the fault code and check live coolant temperature data. Compare the reading to actual engine temperature using an infrared thermometer.

Step 2: Inspect the coolant temperature sensor connector located near the thermostat housing on the engine block. Look for corrosion, moisture intrusion, or damaged pins. Clean connections with electrical contact cleaner and check for proper seating.

Step 3: With the ignition off, disconnect the sensor and test its resistance using a multimeter. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms. If readings are out of specification or show infinite resistance, replace the sensor.

Step 4: For used excavators, thoroughly inspect the wiring harness from sensor to ECM for chafing points, especially where it routes near moving components or sharp edges. Repair any damaged insulation with heat-shrink tubing and relocate the harness if necessary.

Step 5: Clear the fault code and test operation under normal working conditions for at least 30 minutes to confirm the repair.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine and consider professional diagnostic assistance for complex electrical issues.