Komatsu PC60-8 Fault Code E-20: Complete Diagnostic Guide

What is Komatsu PC60-8 Fault Code E-20?

Fault Code E-20 on the Komatsu PC60-8 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading. This code is triggered when the Engine Control Module (ECM) detects voltage signals outside the normal operating range from the coolant temperature sensor, typically between 0.5-4.5 volts.

The coolant temperature sensor is critical for the PC60-8's performance because it directly influences fuel injection timing, engine warm-up cycles, and prevents overheating damage. When this sensor fails or provides incorrect data, the ECM may default to safe mode, limiting machine performance to protect the engine from potential thermal damage.

Common Symptoms

When Code E-20 is active, operators typically experience:

• Warning light illumination on the instrument panel, often accompanied by an audible alarm
• Hard starting conditions, especially during cold weather operation
• Rough idling or irregular engine performance during warm-up
• Reduced engine power or derate mode activation to prevent overheating
• Inaccurate temperature gauge readings showing extreme high or low temperatures that don't match actual engine conditions

Potential Causes

The most common technical causes for E-20 on used PC60-8 excavators include:

• Faulty coolant temperature sensor due to internal resistance drift or element failure (common after 5,000+ operating hours)
• Damaged wiring harness near the thermostat housing where vibration and heat cause insulation breakdown
• Corroded or loose connector pins at the sensor plug, especially on machines exposed to moisture
• Shorted or open circuits in the sensor wiring between the sensor and ECM
• Low coolant levels causing sensor exposure to air rather than coolant
• ECM internal fault (rare, but possible in high-hour machines)

How to Troubleshoot and Fix Code E-20

Step 1: Visual Inspection Begin by checking coolant levels and inspecting the coolant temperature sensor located near the thermostat housing. On used excavators, carefully examine the wiring harness for signs of chafing, heat damage, or oil contamination. Check connector pins for corrosion or bent terminals—a common issue on older PC60-8 models.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms. Test the harness voltage with the key on, engine off—you should see approximately 5 volts reference voltage from the ECM. Check for continuity and shorts to ground in the wiring.

Step 3: Component Replacement and Verification If resistance values are out of specification or the sensor shows physical damage, replace it with a genuine Komatsu part (Part #6732-81-3110 or equivalent). After replacement, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool. Run the engine through a complete warm-up cycle to verify proper operation.

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