Komatsu PC120LC-6 Fault Code E216: Complete Diagnostic Guide

What is Komatsu PC120LC-6 Fault Code E216?

Fault Code E216 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormal voltage signal or open circuit condition in the ECM (Engine Control Module) monitoring system. This code triggers when the ECM receives voltage readings outside the normal operating range of 0.5-4.5 volts from the coolant temperature sensor.

For the PC120LC-6's SAA4D102E-1 engine, accurate coolant temperature monitoring is critical for proper fuel injection timing, idle speed control, and preventing thermal damage. When this sensor circuit fails, the ECM defaults to a predetermined temperature value, potentially causing inefficient combustion, increased emissions, and reduced engine performance.

Common Symptoms

• Warning light illumination on the instrument panel (check engine or malfunction indicator)
• Hard starting conditions, especially during cold starts when enrichment is needed
• Rough idling or inconsistent engine RPM due to improper fuel delivery mapping
• Black smoke from exhaust indicating overfueling from incorrect temperature compensation
• Engine derate mode activation in severe cases, limiting power output to protect components

Potential Causes

The primary causes for E216 in used PC120LC-6 excavators include:

• Coolant temperature sensor failure due to internal element degradation (common after 5,000+ operating hours)
• Wiring harness damage at known rub points near the thermostat housing and along the valve cover
• Corroded or loose connector pins at the sensor plug, especially in machines exposed to moisture
• ECM internal circuit failure (less common but possible in high-hour machines)
• Damaged sensor threads causing improper grounding or coolant leaks affecting readings
• Previous repair attempts using non-OEM sensors with incorrect resistance curves

How to Troubleshoot and Fix Code E216

Step 1: Visual Inspection Locate the coolant temperature sensor on the thermostat housing (driver's side of engine block). Inspect the connector for corrosion, moisture, or bent pins. Check the wiring harness for abrasion damage along routing points near moving components. On used excavators, pay special attention to wire insulation brittleness.

Step 2: Electrical Testing Disconnect the sensor connector. Using a digital multimeter, measure resistance across sensor terminals. At 20°C (68°F), resistance should read approximately 2,500 ohms; at 80°C (176°F), approximately 300 ohms. Values outside ±10% indicate sensor replacement is needed.

Step 3: Circuit Verification With sensor disconnected, check supply voltage at the harness connector: should read 5.0 volts ±0.25V with ignition on. Measure resistance to ground on the signal wire (should exceed 10kΩ). Low resistance indicates harness-to-chassis short.

Step 4: ECM Communication Connect Komatsu KOMTRAX diagnostic software or compatible scan tool. Clear codes and monitor live sensor data while warming the engine. Erratic voltage fluctuations confirm wiring issues; steady but incorrect values suggest sensor failure.

For used excavators: Before replacing components, thoroughly clean all connector contacts with electrical contact cleaner and apply dielectric grease. Check for coolant contamination in connector cavities—a common aging-related issue.

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