Komatsu PC850SE-8R Fault Code E-17: Complete Diagnostic Guide

What is Komatsu PC850SE-8R Fault Code E-17?

Fault Code E-17 on the Komatsu PC850SE-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 regulate fuel injection timing, engine speed, and activate warning systems. On the PC850SE-8R's high-output diesel engine, maintaining proper temperature monitoring is essential for preventing catastrophic engine damage and ensuring optimal hydraulic system performance. When this sensor circuit fails, the ECM cannot accurately assess engine thermal conditions, potentially leading to reduced machine performance or automatic derate modes.

Common Symptoms

When Code E-17 is active, operators typically experience:

• Engine warning light illuminated on the instrument panel, often accompanied by a temperature warning icon
• Engine derate mode activated, limiting maximum RPM and hydraulic power output to protect the engine
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Cooling fan running continuously at high speed, regardless of actual engine temperature
• Difficulty starting in cold conditions, or rough idle during warm-up periods

Potential Causes

The most common technical causes for E-17 on used PC850SE-8R excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling stress
• Damaged wiring harness near the sensor connector, particularly where the harness routes along the engine block (known rub point on this model)
• Corroded or loose electrical connectors at the sensor or ECM interface, common in machines with high operating hours
• ECM internal circuit failure affecting the temperature input channel
• Coolant system issues causing actual overheating conditions that trigger the sensor threshold
• Poor ground connections in the engine sensor ground circuit

How to Troubleshoot and Fix Code E-17

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block's coolant outlet housing. Check for physical damage, coolant leaks around the sensor, and examine the wiring harness for chafing, cuts, or heat damage. On used excavators, pay special attention to connector pins for corrosion or bent terminals.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at ambient temperature (typically 2,000-3,000 ohms at 20°C for Komatsu sensors). Compare readings against manufacturer specifications. Test the harness continuity from sensor connector to ECM, checking for opens or shorts to ground. Verify supply voltage (typically 5V reference) at the sensor connector with ignition on.

Step 3: Advanced Diagnostics Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to read live sensor data and compare actual coolant temperature against sensor output. Check for intermittent connection issues by wiggling harnesses while monitoring data. Inspect the ECM ground connections and clean all ground points thoroughly—a common issue in high-hour machines.

Step 4: Component Replacement If sensor resistance is out of specification or harness damage is found, replace the faulty component using genuine Komatsu parts. For used excavators, always replace the connector pigtail if any corrosion is present, as this prevents recurring failures. After repairs, clear codes and perform a heat cycle test to verify proper operation.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional assistance from certified Komatsu technicians for complex electrical diagnostics or if you're uncertain about any procedure.