Komatsu PC850-8R Fault Code E-14: Complete Diagnostic Guide

What is Komatsu PC850-8R Fault Code E-14?

Fault Code E-14 on the Komatsu PC850-8R indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Engine Control Module (ECM). This code specifically relates to the temperature monitoring system that protects the engine from overheating damage.

The coolant temperature sensor provides critical data to the ECM, which uses this information to adjust fuel injection timing, control engine speed, and activate warning systems. On the PC850-8R's SAA6D170E-5 engine, maintaining proper temperature monitoring is essential for preventing catastrophic engine damage and ensuring optimal hydraulic system performance. When this code triggers, the machine may enter a protective derate mode to prevent overheating.

Common Symptoms

When Code E-14 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Reduced engine power or automatic derate limiting machine performance to 70-80% capacity
• Erratic temperature gauge readings showing unusually high, low, or fluctuating coolant temperatures
• Difficulty starting in cold conditions if the ECM receives incorrect temperature data
• Increased fan engagement as the system attempts to compensate for perceived overheating

Potential Causes

The most common technical causes for E-14 on used PC850-8R excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal element breakdown
• Damaged wiring harness near the engine block where vibration and heat cause insulation wear
• Corroded or loose connector pins at the sensor plug, especially on machines operating in wet or coastal environments
• ECM internal fault affecting the temperature monitoring circuit (less common)
• Coolant contamination causing sensor element fouling or coating
• Ground circuit issues creating intermittent signal loss

How to Troubleshoot and Fix Code E-14

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing). Inspect the wiring harness for obvious damage, chafing, or melted insulation. On used excavators, pay special attention to areas where the harness contacts metal surfaces or passes near hot exhaust components. Check the connector for corrosion, bent pins, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At room temperature (20°C/68°F), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness continuity from the sensor connector back to the ECM. Check for proper ground circuit integrity, as poor grounding is a frequent issue in older machines.

Step 3: Live Data Analysis Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to monitor real-time temperature readings. Compare the sensor reading to actual coolant temperature using an infrared thermometer. A variance greater than 10°C indicates sensor failure. Clear the code and monitor for recurrence during a heat cycle.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu temperature sensor (Part #6754-81-6120 or equivalent). For used excavators, always replace the connector pigtail simultaneously if any corrosion is present, as this prevents future intermittent faults. Apply dielectric grease to connections before reassembly.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC850-8R service manual and consider professional assistance for complex electrical diagnostics. Improper repairs may void warranties or cause additional damage.