Komatsu PC800-7 Fault Code E-17: Complete Diagnostic Guide

What is Komatsu PC800-7 Fault Code E-17?

Fault Code E-17 on the Komatsu PC800-7 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 sensor sending irregular voltage signals outside the manufacturer's specified parameters, typically between 0.5-4.5 volts.

This fault is critical for the PC800-7's performance because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, control engine warm-up cycles, and prevent overheating damage to the SAA6D140E-3 engine. When E-17 triggers, the ECM may default to a predetermined temperature value, potentially causing inefficient combustion, increased emissions, and reduced hydraulic system performance.

Common Symptoms

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

• Engine warning light illuminated on the monitor panel with E-17 displayed
• Hard starting or extended cranking time, especially in cold conditions
• Black or white exhaust smoke due to improper fuel-air mixture calculations
• Engine derate mode activating, limiting maximum RPM to protect components
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions

Potential Causes

The most common technical reasons for E-17 on used PC800-7 excavators include:

• Coolant temperature sensor failure due to internal element degradation (common after 8,000+ operating hours)
• Corroded or loose connector pins at the sensor harness connection point near the thermostat housing
• Damaged wiring harness from rubbing against the engine block or hydraulic lines—particularly at the routing point behind the fuel filter assembly
• Contaminated coolant causing sensor element coating and false readings
• ECM internal fault or corrupted calibration data (less common but possible in high-hour machines)
• Poor ground connection at the sensor circuit ground point on the cylinder head

How to Troubleshoot and Fix Code E-17

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the left side of the cylinder head near the thermostat housing. Check for coolant leaks, corrosion on the connector, and physical damage. On used excavators, examine the wiring harness for wear points where it contacts metal surfaces—this is a known issue on PC800-7 models with 5,000+ hours.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms. Test the harness voltage with the key on, engine off—you should see approximately 5 volts supply from the ECM. Check continuity between the sensor ground wire and chassis ground (should be less than 1 ohm).

Step 3: Advanced Diagnostics Connect Komatsu KOMTRAX or compatible diagnostic software to monitor live coolant temperature data. Compare the sensor reading against an infrared thermometer measurement of the actual coolant temperature. A variance greater than 10°F indicates sensor replacement is necessary. Clear the code and monitor for recurrence—intermittent codes often indicate connector corrosion rather than sensor failure.

Step 4: Repair and Verification Replace the faulty component (sensor costs approximately $45-85 OEM). Apply dielectric grease to connector pins before reassembly to prevent future corrosion. After repairs, perform a complete warm-up cycle and verify the code doesn't return using diagnostic software.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic services for complex electrical issues or if you're unfamiliar with high-voltage systems.