Komatsu PC750SE-7 Fault Code E-17: Complete Diagnostic Guide

What is Komatsu PC750SE-7 Fault Code E-17?

Fault Code E-17 on the Komatsu PC750SE-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 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 adjust fuel injection timing, control engine speed, and activate warning systems. On the PC750SE-7's SAA6D140E-5 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 manage engine protection protocols, potentially leading to severe overheating or unnecessary derating.

Common Symptoms

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

• Engine warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Engine derate mode activated, limiting machine power output and hydraulic performance
• Cooling fan running continuously at maximum speed regardless of actual engine temperature
• Difficulty starting in cold conditions due to improper fuel enrichment calculations

Potential Causes

The most common technical causes for E-17 on used PC750SE-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal element breakdown
• Damaged wiring harness near the engine block where vibration and heat cause insulation wear
• Corroded or loose connector pins at the sensor plug, especially on machines operating in wet or corrosive environments
• Shorted or open circuit in the sensor signal wire between the sensor and ECM
• ECM internal fault (less common) affecting the temperature input circuit
• Coolant contamination causing sensor element coating and inaccurate readings

How to Troubleshoot and Fix Code E-17

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, rubbing points against engine components, or heat damage. On used excavators, check for oil or coolant contamination on connectors, which indicates seal failure.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure sensor resistance. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms (consult service manual for exact specifications). Test the harness continuity from sensor connector to ECM pin, checking for opens or shorts to ground.

Step 3: Live Data Analysis Using Komatsu diagnostic software (KOMTRAX Plus) or compatible scan tool, monitor live coolant temperature data. Compare sensor readings against actual engine temperature using an infrared thermometer. A variance greater than 10°F indicates sensor replacement is necessary.

Step 4: Connector Service Clean all connector pins with electrical contact cleaner and inspect for corrosion or bent terminals—common issues on machines with 5,000+ operating hours. Apply dielectric grease to prevent future moisture intrusion.

Step 5: Component Replacement If testing confirms sensor failure, replace with genuine Komatsu parts (Part #6732-81-3110 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. Always consult the official Komatsu service manual for your specific machine serial number and consider professional assistance for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.