Komatsu PC850SE-8R Fault Code E-13: Complete Diagnostic Guide

What is Komatsu PC850SE-8R Fault Code E-13?

Fault Code E-13 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 temperature monitoring system that protects the engine from overheating damage.

The coolant temperature sensor provides critical data to the ECM, which uses this information to regulate fuel injection timing, engine speed, and activate warning systems. On the PC850SE-8R's high-output diesel engine, maintaining proper temperature monitoring is essential for preventing catastrophic engine damage and ensuring optimal hydraulic system performance. When this sensor circuit fails, the ECM cannot accurately assess engine thermal conditions, potentially leading to reduced machine performance or automatic derate modes.

Common Symptoms

When Code E-13 is active, operators typically experience:

• Engine warning light illuminated on the instrument panel, often accompanied by a temperature warning icon
• Automatic engine derate or power reduction mode, limiting machine performance to prevent potential overheating
• Erratic temperature gauge readings that fluctuate abnormally or show maximum/minimum values regardless of actual engine temperature
• Difficulty starting in cold conditions, as the ECM may default to incorrect fuel mapping
• Increased fan engagement or continuous cooling fan operation due to ECM receiving false high-temperature signals

Potential Causes

The most common technical causes for E-13 on used PC850SE-8R excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling stress
• Damaged wiring harness near the engine block where vibration and heat cause insulation breakdown
• Corroded or loose connector pins at the sensor connection point, particularly common in machines exposed to moisture
• ECM internal circuit issues affecting the temperature input channel
• Intermittent short circuits caused by harness rubbing against engine components or frame members
• Contaminated coolant causing sensor element fouling or corrosion

How to Troubleshoot and Fix Code E-13

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 used excavators, carefully examine the wiring harness from the sensor to the ECM for signs of chafing, melted insulation, or connector damage.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its 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 harness continuity and check for shorts to ground. Measure supply voltage at the connector with ignition on—should read approximately 5 volts.

Step 3: Connector and Ground Verification Clean all connector pins with electrical contact cleaner and inspect for bent terminals. Verify the ground circuit integrity, as poor grounds are common in older machines. Check for voltage drop across ground connections.

Step 4: Component Replacement If sensor resistance is out of specification or harness damage is found, replace the faulty component using OEM Komatsu parts for reliability. After replacement, clear codes using Komatsu diagnostic software (KOMTRAX) and perform a 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 assistance from certified Komatsu technicians for complex electrical diagnostics.