Komatsu PC850-8R Fault Code E-17: Complete Diagnostic Guide

What is Komatsu PC850-8R Fault Code E-17?

Fault Code E-17 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 coolant temperature monitoring system, which is critical for preventing engine overheating and maintaining optimal operating temperatures.

The ECM continuously monitors signals from the coolant temperature sensor to regulate fuel injection timing, fan speed, and engine protection protocols. When the sensor voltage falls outside the manufacturer's specified range (typically 0.5-4.5V), or when the temperature reading exceeds safe parameters, the system triggers E-17. For the PC850-8R's SAA6D170E-5 engine, proper coolant temperature management is essential for maintaining the 400+ horsepower output and preventing catastrophic engine damage in demanding mining and quarry applications.

Common Symptoms

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

• Engine warning light illuminated on the monitor panel with audible alarm
• Reduced engine power (derate mode) to protect against potential overheating
• Erratic temperature gauge readings or gauge stuck at maximum/minimum positions
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Difficulty starting in cold conditions if the ECM receives false low-temperature signals

Potential Causes

The most common technical causes for E-17 on used PC850-8R excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling stress
• Damaged wiring harness near the engine block where vibration and heat cause insulation breakdown
• Corroded or loose connector pins at the sensor or ECM connection points (common in machines operating in wet/corrosive environments)
• Shorted or open circuit in the sensor signal wire, particularly at known rub points near the turbocharger
• Low coolant level causing actual overheating and legitimate high-temperature warnings
• ECM internal fault (less common) affecting the temperature monitoring circuit

How to Troubleshoot and Fix Code E-17

Step 1: Visual Inspection Begin by checking actual coolant level and condition. Inspect the coolant temperature sensor (located on the engine block near the thermostat housing) and its wiring harness for obvious damage, corrosion, or oil contamination. On used excavators, pay special attention to harness routing near hot exhaust components where insulation may have deteriorated.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult your service manual for exact specifications). Check for continuity between the sensor signal wire and ECM pin, and verify no shorts to ground exist.

Step 3: Live Data Analysis Connect Komatsu KOMTRAX diagnostic software or compatible scan tool to monitor live coolant temperature readings. Compare the displayed temperature with an infrared thermometer reading of the actual engine temperature. A variance greater than 10°F indicates sensor replacement is necessary.

Step 4: Connector and Harness Repair For used machines, thoroughly clean all connector pins with electrical contact cleaner and apply dielectric grease to prevent future corrosion. Inspect the harness for wear at mounting brackets and secure any loose sections that may contact moving components.

Step 5: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu coolant temperature sensor (Part #6754-81-6210 or equivalent). After replacement, clear codes using diagnostic software and perform a test cycle to verify proper operation.

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Disclaimer: This guide provides general diagnostic information for Code E-17. Always consult the official Komatsu PC850-8R service manual and consider professional assistance from certified Komatsu technicians for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.