Komatsu PC850-8R Fault Code E-19: Complete Diagnostic Guide

What is Komatsu PC850-8R Fault Code E-19?

Fault Code E-19 on the Komatsu PC850-8R 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, fan speed, and engine protection protocols. When the sensor provides readings outside the normal operating range (typically -40°C to 150°C) or the circuit shows electrical irregularities, the system triggers E-19. For the PC850-8R's high-performance SAA6D170E engine, accurate temperature monitoring is essential to prevent catastrophic engine damage and maintain the 400+ horsepower output under heavy loads.

Common Symptoms

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

• Engine warning light illuminated on the monitor panel with audible alarm
• Reduced engine power or automatic derate mode 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 if the ECM receives incorrect temperature data

Potential Causes

The most common technical causes for E-19 on used PC850-8R 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 frame rails
• Poor ground connections at the sensor or ECM, common in machines with 5,000+ operating hours
• Coolant contamination causing sensor coating or electrical resistance changes
• ECM internal fault or corrupted calibration data (less common but possible in older units)
• Aftermarket coolant incompatible with sensor specifications

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, or corrosion on the connector pins. On used excavators, examine the entire wiring harness from sensor to ECM for chafing, particularly 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 circuit continuity from sensor connector to ECM and verify ground integrity (should read less than 1 ohm resistance).

Step 3: Live Data Analysis Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to monitor real-time coolant temperature readings. Compare sensor output against actual engine temperature using an infrared thermometer. A variance greater than 10°C indicates sensor failure.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu part (P/N 6754-61-6210 or equivalent). For used machines, always replace the connector pigtail simultaneously, as corrosion often extends into the wire strands. Apply dielectric grease to new connections to prevent future corrosion.

Step 5: System Reset and Verification After repairs, clear fault codes using diagnostic software and run the engine through a complete heat cycle. Monitor for code recurrence and verify proper cooling fan operation and temperature gauge accuracy.

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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 uncertain about any procedure.