Komatsu PC750-7 Fault Code E-17: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E-17?

Fault Code E-17 on the Komatsu PC750-7 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 system, which monitors engine operating temperature and sends critical data to the ECM for fuel injection timing, fan control, and engine protection protocols.

This fault is particularly critical for the PC750-7's SAA6D140E-3 engine because improper temperature readings can lead to inadequate cooling system response, potential engine overheating, or unnecessary derating. The ECM relies on accurate coolant temperature data to optimize combustion efficiency and prevent catastrophic engine damage in this 400+ horsepower machine.

Common Symptoms

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

• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Engine derate mode activation, limiting power output to protect the engine from perceived overheating
• Cooling fan running continuously at maximum speed, regardless of actual engine temperature
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Difficulty starting in cold conditions if the ECM receives false cold-temperature signals

Potential Causes

The most common technical causes for E-17 on used PC750-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling damage
• Wiring harness damage at known rub points near the engine block or along the frame rail
• Corroded or loose connector pins at the sensor or ECM connection points (common in machines with 5,000+ hours)
• ECM internal circuit failure affecting the temperature sensor input channel
• Coolant contamination causing sensor element fouling or coating
• Ground circuit issues creating voltage reference problems in the sensor circuit

How to Troubleshoot and Fix Code E-17

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block's coolant passage. Check for physical damage, coolant leaks around the sensor base, and corrosion on the connector. On used excavators, examine the wiring harness from sensor to ECM for abrasion points, especially where it contacts frame members or passes through bulkheads.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at ambient temperature (typically 2,000-3,000 ohms at 20°C for Komatsu sensors). Compare readings against manufacturer specifications. Check supply voltage at the sensor connector (should be approximately 5 volts from the ECM). Verify ground circuit continuity with less than 1 ohm resistance.

Step 3: Circuit Verification With the sensor disconnected, check for short circuits between signal and ground wires. Inspect ECM connector pins for corrosion, bent terminals, or moisture intrusion—critical on machines operating in harsh environments. Use Komatsu KOMTRAX or compatible diagnostic software to monitor live sensor data and compare against actual coolant temperature.

Step 4: Component Replacement If sensor resistance is out of specification or wiring shows damage, replace the faulty component. For used machines, always replace connector seals and apply dielectric grease to prevent future corrosion. After repairs, clear codes and perform a heat cycle test to verify proper operation.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC750-7 service manual and consider professional technician assistance for complex electrical diagnostics or ECM-related issues.