Komatsu PC800-7 Fault Code E117: Complete Diagnostic Guide

What is Komatsu PC800-7 Fault Code E117?

Fault Code E117 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.

The coolant temperature sensor is critical for the PC800-7's performance because the ECM uses this data to adjust fuel injection timing, control engine warm-up cycles, and prevent overheating damage to the SAA6D140E-5 engine. When this sensor fails or provides inaccurate readings, the machine may enter derate mode to protect engine components, significantly reducing productivity on job sites.

Common Symptoms

When Code E117 is active, operators typically experience:

• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Engine derate or reduced power output, limiting hydraulic performance and travel speed
• Hard starting conditions, especially during cold weather operation
• Erratic engine idle or rough running as the ECM compensates for missing temperature data
• Cooling fan running continuously at high speed, regardless of actual engine temperature

Potential Causes

The most common technical reasons for E117 on used PC800-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal element breakdown
• Wiring harness damage at known rub points near the engine block or along the chassis rail
• Corroded or loose connector pins at the sensor plug, especially on machines operating in harsh environments
• ECM internal circuit failure affecting the sensor input channel (less common)
• Damaged sensor mounting threads causing coolant leaks and sensor exposure to air
• Aftermarket sensor incompatibility if previous repairs used non-OEM components

How to Troubleshoot and Fix Code E117

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 oil contamination. On used excavators, pay special attention to areas where harnesses contact metal surfaces or moving components.

Step 2: Connector and Resistance Testing Disconnect the sensor connector and inspect for corrosion, bent pins, or moisture intrusion. Using a digital multimeter, measure sensor resistance at ambient temperature—it should read approximately 2,000-3,000 ohms at 20°C (68°F). Compare readings against Komatsu's specification chart for temperature-to-resistance values.

Step 3: Circuit Voltage Check With the connector still disconnected and ignition ON, measure voltage at the ECM side of the harness. You should see approximately 5 volts reference voltage. If voltage is absent or incorrect, trace the harness back to the ECM for breaks or shorts to ground.

Step 4: Sensor Replacement and Verification If testing confirms sensor failure, replace with a genuine Komatsu sensor (Part #6754-61-6210 or equivalent). Apply thread sealant to prevent coolant leaks. After installation, clear codes using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then monitor for code recurrence during a complete heat cycle.

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