Komatsu PC450LC-6 Fault Code E106: Complete Diagnostic Guide

What is Komatsu PC450LC-6 Fault Code E106?

Fault Code E106 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 SAA6D125E-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. When the ECM detects voltage readings outside the normal range (typically 0.5-4.5V) or physically impossible temperature values, it triggers E106. This is critical for the PC450LC-6 because improper temperature management can lead to severe engine damage, reduced hydraulic efficiency, and costly downtime on used machines where cooling system components may already be degraded.

Common Symptoms

When Code E106 is active, operators typically experience:

• Warning light illumination on the monitor panel with possible audible alarm
• Engine derate mode where maximum RPM is limited to protect the engine
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Difficulty starting in cold conditions or excessive white smoke during warm-up

Potential Causes

The most common technical causes for E106 on used PC450LC-6 excavators include:

• Coolant temperature sensor failure due to age-related internal resistance drift or element corrosion
• Wiring harness damage at known rub points near the engine block mounting brackets or along the frame rail
• Corroded or loose connector pins at the sensor plug (2-pin connector), especially on machines operating in harsh environments
• ECM internal circuit degradation affecting the 5V reference voltage supply
• Coolant contamination causing sensor element coating or failure
• Aftermarket sensor incompatibility if previously replaced with non-OEM parts

How to Troubleshoot and Fix Code E106

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block's thermostat housing. Check for physical damage, coolant leaks, or corrosion on the connector terminals. On used excavators, examine the entire wiring harness from sensor to ECM for chafing, especially where it contacts metal edges or moves with engine vibration.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult service manual for exact specifications). Test the harness continuity from the ECM connector to the sensor plug, checking for opens or shorts to ground.

Step 3: Reference Voltage Check With the sensor disconnected and ignition on, measure voltage at the harness connector. You should see approximately 5V reference voltage from the ECM. If voltage is absent or incorrect, suspect ECM issues or harness problems rather than the sensor itself.

Step 4: Replacement and Verification Install a genuine Komatsu coolant temperature sensor (Part #6732-81-3210 or equivalent). Clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool. Run the engine through temperature cycles and monitor for code recurrence.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC450LC-6 service manual and consider professional assistance from certified Komatsu technicians for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.