Komatsu PC130-6 Fault Code H-15: Complete Diagnostic Guide

What is Komatsu PC130-6 Fault Code H-15?

Fault Code H-15 on the Komatsu PC130-6 indicates a malfunction in the engine coolant temperature sensor circuit. This code is triggered when the ECM (Engine Control Module) detects an abnormal signal—either out of range high, out of range low, or an open/short circuit condition—from the coolant temperature sensor.

The coolant temperature sensor is a critical component that provides real-time data to the ECM for fuel injection timing, cold start enrichment, and cooling fan activation. On the PC130-6's 6D95L engine, accurate coolant temperature readings are essential for proper combustion efficiency and preventing thermal damage.

When this sensor fails, the ECM cannot accurately manage engine parameters, potentially leading to poor fuel economy, increased emissions, and risk of overheating.

Common Symptoms

• Warning lamp illuminated on the monitor panel
• Engine running in default/limp mode with reduced performance
• Erratic or non-functional temperature gauge readings
• Cooling fan running continuously or not engaging at all
• Difficulty starting in cold conditions due to improper fuel enrichment

Potential Causes

The most common causes for H-15 on used PC130-6 excavators include:

• Sensor failure due to age and thermal cycling degradation
• Corroded or damaged connector pins at the sensor harness
• Wiring harness chafing near the engine block or firewall routing points
• Open or short circuit in the signal wire between sensor and ECM
• Contaminated coolant causing sensor element fouling

How to Troubleshoot and Fix Code H-15

Step 1: Visual Inspection Locate the coolant temperature sensor on the engine block. Inspect the connector for corrosion, moisture intrusion, or bent pins. On used excavators, check for harness wear where wiring routes near hot surfaces or moving components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 20°C (68°F), expect approximately 2.0-3.0 kΩ. At 80°C (176°F), resistance should drop to 200-400 ohms. Values outside this range indicate sensor failure.

Step 3: Circuit Integrity Check With the sensor disconnected, check for continuity between the sensor connector and ECM terminals. Verify there are no shorts to ground or to the 5V reference circuit. Repair any damaged wiring before proceeding.

Step 4: Component Replacement If the sensor tests faulty, replace with an OEM-specification unit. Clear the fault code using Komatsu diagnostic software or by disconnecting the battery for several minutes, then verify proper operation.

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Disclaimer: This guide is for informational purposes. Complex electrical diagnostics should be performed by qualified technicians using manufacturer-approved procedures and equipment.