Komatsu PC750LC-7 Fault Code E-19: Complete Diagnostic Guide

What is Komatsu PC750LC-7 Fault Code E-19?

Fault Code E-19 on the Komatsu PC750LC-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 monitoring system, which is critical for preventing engine overheating and maintaining optimal operating temperatures.

The ECM continuously monitors signals from the coolant temperature sensor to regulate fuel injection timing, engine speed, and cooling fan operation. When the sensor provides readings outside the normal operating range (typically -40°F to 300°F), or when circuit voltage falls outside specified parameters (usually 0.5V to 4.5V), the E-19 code triggers. For the PC750LC-7's SAA6D140E-3 engine, proper temperature monitoring is essential to prevent catastrophic engine damage and maintain the machine's 400+ horsepower output efficiently.

Common Symptoms

When Code E-19 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel with accompanying audible alarm
• Reduced engine power or automatic derate mode to protect the engine from potential overheating
• Inaccurate temperature gauge readings showing extremely high, low, or erratic temperatures
• Cooling fan running continuously at maximum speed regardless of actual engine temperature
• Difficulty starting in cold conditions or poor engine performance during warm-up

Potential Causes

The most common technical causes for E-19 on used PC750LC-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, particularly where the harness routes near the engine block
• Corroded sensor connector pins caused by coolant leaks or moisture intrusion in the engine compartment
• Broken or chafed wires at known rub points near the fuel injection pump mounting bracket
• ECM internal fault (rare, but possible in high-hour machines)
• Poor ground connection at the sensor or ECM ground points
• Coolant contamination affecting sensor accuracy

How to Troubleshoot and Fix Code E-19

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 corrosion. On used excavators, pay special attention to areas where harnesses contact metal surfaces or moving components. Check for coolant leaks that may have contaminated electrical connections.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Check circuit voltage at the harness connector with ignition on—you should see approximately 5V reference voltage from the ECM.

Step 3: Circuit Continuity Check Test continuity between the sensor connector and ECM pins using wiring diagrams. Check for shorts to ground or power. Inspect all ground connections and clean contact surfaces thoroughly, as corrosion is common in older machines.

Step 4: Component Replacement If sensor resistance is out of specification or circuit testing reveals wiring faults, replace the defective component. For used excavators, consider replacing both the sensor and connector as preventive maintenance. After repairs, clear codes using Komatsu diagnostic software (KOMTRAX) and verify proper operation through a complete heat cycle.

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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 uncertain about any procedure.