Komatsu PC850SE-8R Fault Code E-19: Complete Diagnostic Guide

What is Komatsu PC850SE-8R Fault Code E-19?

Fault Code E-19 on the Komatsu PC850SE-8R 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°C to 150°C), or when circuit voltage falls outside specified parameters (usually 0.5V to 4.5V), the system triggers E-19. For the PC850SE-8R's high-output diesel engine, accurate temperature monitoring is essential to prevent catastrophic engine damage and maintain the machine's 850-horsepower performance capability.

Common Symptoms

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

• Engine warning light illuminated on the instrument cluster with possible audible alarm
• Reduced engine power or derate mode activation to protect the engine from potential overheating
• Erratic temperature gauge readings showing unusually high, low, or fluctuating coolant temperatures
• Cooling fan running continuously at maximum speed regardless of actual engine temperature
• Difficulty starting in cold conditions or rough idle when the engine is cold

Potential Causes

The most common technical causes for E-19 on used PC850SE-8R excavators include:

• Faulty coolant temperature sensor due to internal element degradation or contamination from coolant additives
• Damaged wiring harness or corroded connectors, particularly at rub points near the engine block or along the main harness routing
• Coolant contamination or low coolant level affecting sensor accuracy
• ECM internal fault or corrupted calibration data (less common)
• Poor ground connections at the sensor or ECM mounting points
• Aftermarket coolant incompatible with sensor specifications causing premature failure

How to Troubleshoot and Fix Code E-19

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block (typically near the thermostat housing). Check for physical damage, coolant leaks, or corrosion on the connector pins. On used excavators, examine the entire wiring harness from sensor to ECM for chafing, particularly where it contacts the engine or frame.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 20°C (68°F), resistance should typically read 2,000-3,000 ohms (consult 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: Signal and Ground Verification Test ground continuity between the sensor ground wire and chassis ground (should be less than 1 ohm). With the sensor reconnected, use Komatsu diagnostic software (KOMTRAX) or a compatible scan tool to monitor live coolant temperature data and compare it against actual engine temperature using an infrared thermometer.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu sensor (part number specific to PC850SE-8R). For used machines, always apply dielectric grease to connector pins to prevent future corrosion. Clear the fault code and perform a complete operational test cycle.

---

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues or if you're unfamiliar with high-voltage systems.