Komatsu PC100-6 Fault Code E306: Complete Diagnostic Guide

What is Komatsu PC100-6 Fault Code E306?

Fault Code E306 indicates a malfunction in the engine coolant temperature sensor circuit. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal from the coolant temperature sensor, typically reading either too high (open circuit) or too low (short circuit) compared to specified parameters.

The coolant temperature sensor is critical for the PC100-6's fuel injection timing, engine protection systems, and overall performance optimization. When this sensor fails, the ECM cannot accurately monitor engine temperature, potentially leading to improper fuel delivery, reduced efficiency, and risk of engine overheating without proper warning.

Common Symptoms

When Code E306 is active, operators typically experience:

• Engine warning light illuminated on the instrument panel
• Hard starting or extended cranking time, especially in cold conditions
• Poor fuel economy due to incorrect fuel map operation
• Black smoke from exhaust caused by rich fuel mixture compensation
• Engine running in default/limp mode with limited power output until restart

Potential Causes

On used Komatsu PC100-6 excavators, E306 commonly results from:

• Corroded or damaged sensor connector – particularly common due to exposure to engine bay heat cycles and moisture
• Failed coolant temperature sensor – typical lifespan issues on machines with 5,000+ operating hours
• Wiring harness damage – check near engine mount points where vibration causes wire chafing
• ECM internal fault – rare, but possible on higher-hour machines
• Poor electrical ground connections at sensor mounting location due to corrosion buildup

How to Troubleshoot and Fix Code E306

Step 1: Visual Inspection Locate the coolant temperature sensor on the engine block (typically near the thermostat housing). Inspect the connector for corrosion, moisture, or physical damage. On used machines, check for green corrosion on pins—a common failure point.

Step 2: Electrical Testing Using a multimeter, disconnect the sensor and measure resistance. At 68°F (20°C), resistance should read approximately 2.3-2.7 kΩ. Compare readings against Komatsu specifications. Also check circuit voltage with the key on, engine off—should read approximately 5 volts at the connector.

Step 3: Wiring Harness Check Trace the sensor wiring harness from the sensor to the ECM, checking for worn insulation, especially where harnesses contact metal edges or pass near hot exhaust components. Perform continuity and ground fault tests.

Step 4: Component Replacement If sensor tests fail specifications, replace with a genuine Komatsu part. Clean the sensor mounting threads and apply anti-seize compound. After installation, clear codes using Komatsu diagnostic software and verify proper operation.

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Disclaimer: This guide provides general troubleshooting information. Always consult qualified diesel technicians and official Komatsu service documentation for your specific machine. Improper diagnosis may lead to further damage or safety hazards.