Komatsu PC800SE-7 Fault Code E117: Complete Diagnostic Guide

What is Komatsu PC800SE-7 Fault Code E117?

Fault Code E117 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 Komatsu SAA6D140E-7 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 PC800SE-7, this sensor is vital for maintaining optimal engine performance and preventing catastrophic thermal damage to cylinder heads, gaskets, and pistons. When E117 triggers, the ECM may enter a protective derate mode to prevent engine damage.

Common Symptoms

When Code E117 is active, operators typically experience:

• Engine warning light or check engine light illuminated on the monitor panel
• Engine power reduction (derate mode) limiting machine performance and hydraulic response
• Inaccurate temperature gauge readings showing erratic or frozen temperature displays
• Difficulty starting when the engine is cold, as the ECM cannot properly adjust fuel delivery
• Excessive white smoke during startup due to improper fuel-air mixture calculations

Potential Causes

The most common technical causes for E117 on used PC800SE-7 excavators include:

• Faulty coolant temperature sensor due to internal element degradation (common after 8,000+ operating hours)
• Damaged or corroded wiring harness at connector points, especially near the engine block where heat and vibration cause wear
• Loose or corroded electrical connections at the sensor plug or ECM terminals
• Shorted or open circuit in the sensor wiring, often from harness rubbing against engine components
• Low coolant level causing sensor exposure to air rather than coolant
• ECM internal fault (rare, but possible in high-hour machines)

How to Troubleshoot and Fix Code E117

Step 1: Visual Inspection Begin by checking coolant level in the radiator and overflow tank. Inspect the coolant temperature sensor (located on the engine block near the thermostat housing) for physical damage, coolant leaks, or corrosion. On used excavators, carefully examine the wiring harness for signs of rubbing, cracking, or heat damage along its entire length.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 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 sensor connector to ECM. Check for voltage supply (typically 5V reference) from the ECM with the key on, engine off.

Step 3: Component Replacement and Verification If resistance values are out of specification or the sensor shows corrosion, replace the coolant temperature sensor with a genuine Komatsu part. Clean all connector terminals with electrical contact cleaner and apply dielectric grease. For used machines, inspect connector pins for bent or pushed-back terminals—a common issue causing intermittent codes. Clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then monitor for code recurrence during operation.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number. If you're uncomfortable performing electrical diagnostics, contact a certified Komatsu technician to prevent further damage.