Komatsu PC750SE-7 Fault Code E-19: Complete Diagnostic Guide

What is Komatsu PC750SE-7 Fault Code E-19?

Fault Code E-19 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 sends voltage signals to the ECM, which uses this data to regulate fuel injection timing, engine speed, and activate warning systems. On the PC750SE-7's SAA6D140E-5 engine, maintaining accurate temperature readings is critical for preventing catastrophic engine damage and ensuring optimal hydraulic system performance. When this sensor circuit fails, the ECM cannot properly manage engine protection protocols, potentially leading to severe overheating or unnecessary engine derating.

Common Symptoms

When Code E-19 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 and hydraulic flow
• Cooling fan running continuously at maximum speed regardless of actual engine temperature
• Difficulty starting when the engine is cold, as the ECM defaults to incorrect fuel mapping

Potential Causes

The most common technical reasons for E-19 on used PC750SE-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal short circuits
• Damaged wiring harness near the sensor connector, particularly where the harness routes along the engine block (known rub point on this model)
• Corroded or loose connector pins at the sensor or ECM connection points
• ECM internal fault affecting the temperature input circuit (less common)
• Coolant contamination causing sensor element fouling or premature failure
• Incorrect sensor installation after previous repairs, including wrong torque or missing heat-conductive paste

How to Troubleshoot and Fix Code E-19

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 examine the wiring harness for abrasion, cuts, or heat damage. On used excavators, pay special attention to connector corrosion—disconnect and inspect all pins for green oxidation or bent terminals.

Step 2: Electrical Testing Using a digital multimeter, measure the sensor's resistance. At room temperature (20°C/68°F), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Test the supply voltage at the sensor connector with the key on—you should see approximately 5 volts from the ECM. Check for continuity in the wiring harness between the sensor and ECM connector.

Step 3: Component Replacement and Verification If resistance values are out of specification or wiring shows damage, replace the faulty component. For used machines, always replace the sensor O-ring and apply dielectric grease to connector pins to prevent future corrosion. After repairs, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then monitor the system during a complete heat cycle.

Critical Note for Used Equipment: Before replacing the sensor, inspect the engine coolant condition—contaminated coolant accelerates sensor failure. Check harness routing for modifications from previous repairs that may cause new wear points.

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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 seek professional assistance from certified technicians for complex repairs or if you're unsure about any procedure.