Komatsu PC120LC-6 Fault Code E215: Complete Diagnostic Guide

What is Komatsu PC120LC-6 Fault Code E215?

Fault Code E215 on the Komatsu PC120LC-6 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormally high or open circuit condition. This code is triggered when the ECM (Engine Control Module) receives voltage readings outside the normal operating range from the coolant temperature sensor, typically above 4.9 volts.

The coolant temperature sensor is critical for the PC120LC-6's 6D95L engine operation. It provides essential data for fuel injection timing, cold-start enrichment, and cooling fan activation. When this sensor circuit fails, the ECM cannot accurately regulate combustion parameters, potentially leading to engine damage from overheating or inefficient fuel consumption.

Common Symptoms

• Check Engine or Monitor Panel Warning Light illuminated continuously
• Engine running in derate mode with reduced power output
• Cooling fan running constantly or not engaging at all
• Poor cold-start performance and rough idle conditions
• Inaccurate temperature gauge readings on the operator display

Potential Causes

The most frequent causes of E215 on used PC120LC-6 units include:

• Failed coolant temperature sensor due to thermal cycling degradation
• Open or corroded wiring in the sensor harness, particularly near the exhaust manifold routing
• Damaged connector pins at the ECM or sensor connection points
• Chafed harness where wiring contacts the engine block or frame brackets
• ECM ground circuit issues causing erratic voltage readings

On older machines, harness deterioration from heat exposure and vibration is extremely common around the 8,000+ hour mark.

How to Troubleshoot and Fix Code E215

Step 1: Visual Inspection Locate the coolant temperature sensor on the thermostat housing. Inspect the connector for corrosion, moisture intrusion, or bent pins. Check the wiring harness routing for abrasion points against metal surfaces—this is essential on used excavators before replacing components.

Step 2: Electrical Testing Using a multimeter, measure resistance across the sensor terminals (disconnected). At 20°C (68°F), expect approximately 2.5-3.0 kΩ. Verify 5V reference voltage and proper ground at the harness connector with the key on.

Step 3: Harness Continuity Check Test continuity from the sensor connector to the ECM pins (typically pins 45 and 46 on PC120LC-6). Resistance should read below 5 ohms. Any open circuit indicates harness damage requiring repair or replacement.

Step 4: Component Replacement If testing confirms sensor failure, replace with OEM-specification sensor (Komatsu part number 6732-81-3120 or equivalent). Clear codes using Komatsu diagnostic software (VHMS/DST-i) and verify repair.

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Disclaimer: This guide provides general diagnostic information. Always consult official Komatsu service literature and qualified technicians for complex repairs. Improper diagnostics may cause additional damage or safety hazards.