Komatsu PC750LC-7 Fault Code E113: Complete Diagnostic Guide

What is Komatsu PC750LC-7 Fault Code E113?

Fault Code E113 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 Komatsu SAA6D140E-3 engine from overheating damage.

The coolant temperature sensor sends voltage signals to the ECM, which uses this data to regulate fuel injection timing, fan speed, and engine protection protocols. On the PC750LC-7, this system is critical because the high-output diesel engine generates substantial heat during heavy excavation work. When E113 triggers, the ECM may activate protective measures that limit machine performance to prevent catastrophic engine damage.

Common Symptoms

When Code E113 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Reduced engine power or automatic derate mode, limiting hydraulic performance and digging force
• Cooling fan running continuously at high speed, even when engine temperature appears normal
• Inaccurate temperature gauge readings on the dashboard, showing erratic or frozen values
• Difficulty starting in cold conditions if the ECM receives false low-temperature signals

Potential Causes

The most common technical reasons for E113 on used PC750LC-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling stress
• Damaged wiring harness near the sensor connector, particularly where the harness routes along the engine block (a known wear point on this model)
• Corroded or loose electrical connectors at the sensor or ECM interface, common in machines with high operating hours
• ECM internal fault affecting the temperature monitoring circuit
• Actual engine overheating caused by cooling system failures (low coolant, failed thermostat, clogged radiator)

How to Troubleshoot and Fix Code E113

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block near the thermostat housing. Check for physical damage, coolant leaks around the sensor, and examine the wiring harness for abrasion, cuts, or signs of heat damage. On used excavators, pay special attention to harness routing where it contacts metal surfaces—friction wear is common after 5,000+ operating hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness continuity from sensor connector to ECM, checking for opens or shorts to ground. Measure supply voltage at the sensor connector with ignition on—should read approximately 5 volts.

Step 3: Connector and Ground Verification Clean all electrical connectors with contact cleaner and inspect for corrosion or bent pins. Verify the engine ground straps are secure and free from corrosion, as poor grounding causes erratic sensor readings on older machines.

Step 4: Component Replacement and Verification If testing confirms sensor failure, replace with a genuine Komatsu sensor or OEM-equivalent part. After replacement, clear codes using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then monitor during operation to confirm the fix.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number. If you're uncomfortable performing electrical diagnostics, contact a certified Komatsu technician to prevent further damage to your equipment.