Komatsu PC110-7 Fault Code E-6: Complete Diagnostic Guide

What is Komatsu PC110-7 Fault Code E-6?

Fault Code E-6 on the Komatsu PC110-7 indicates a malfunction in the engine coolant temperature sensor circuit. This code triggers when the Electronic Control Module (ECM) detects an abnormal voltage reading from the water temperature sensor, typically caused by an open circuit, short circuit, or sensor degradation.

The coolant temperature sensor plays a critical role in the PC110-7's SAA4D95LE-3 engine management system. It directly affects fuel injection timing, glow plug operation, and engine protection protocols. When this sensor fails, the ECM cannot accurately monitor engine temperature, potentially leading to overheating damage or inefficient combustion in this mid-sized excavator.

Common Symptoms

Operators experiencing Code E-6 on their Komatsu PC110-7 will typically notice:

• Warning lamp illumination on the instrument cluster with simultaneous engine derating
• Hard starting conditions, especially in cold weather, due to improper glow plug activation
• Erratic temperature gauge readings or gauge stuck at maximum/minimum positions
• Black smoke from exhaust caused by incorrect fuel-air mixture compensation
• Automatic engine shutdown in severe cases when ECM enters protection mode

Potential Causes

The most common technical failures triggering E-6 on used PC110-7 excavators include:

• Corroded or loose connector pins at the coolant temperature sensor (located on the thermostat housing)
• Damaged wiring harness between sensor and ECM, particularly where the harness passes near the engine mount—a known rub point on this model
• Failed coolant temperature sensor due to age-related resistance drift (common after 5,000+ operating hours)
• ECM internal circuit degradation affecting the 5-volt reference supply to the sensor
• Coolant contamination causing sensor element coating and electrical resistance changes
• Previous repair attempts using non-OEM sensors with incorrect resistance curves

How to Troubleshoot and Fix Code E-6

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor connector located on the engine's left side near the thermostat. Check for corrosion, bent pins, moisture intrusion, or oil contamination. On used excavators, this connector frequently suffers from coolant seepage. Clean contacts with electrical contact cleaner and apply dielectric grease.

Step 2: Sensor Resistance Testing Disconnect the sensor and measure resistance across its terminals using a digital multimeter (DMM). At 20°C (68°F), resistance should read approximately 2.3-2.7 kΩ. At 80°C (176°F), expect 0.3-0.4 kΩ. Values outside this range confirm sensor failure requiring replacement with Komatsu OEM part 6732-81-3140.

Step 3: Wiring Harness Verification Check continuity from the sensor connector to ECM pins 18 and 19 (signal and ground). Resistance should be less than 5 ohms. Inspect the harness routing near the engine mount bracket—this is a critical wear point. Look for insulation damage where the harness contacts metal surfaces during engine vibration.

Step 4: Voltage Supply Check With ignition on and sensor disconnected, measure voltage at the harness connector. You should see approximately 5 volts DC on the signal wire. No voltage indicates an ECM power supply fault or broken wire.

Step 5: Code Clearing and Verification After repairs, clear codes using Komatsu KOMTRAX diagnostic software or a compatible scan tool. Run the engine through a complete warm-up cycle (cold to operating temperature) and verify the code doesn't return.

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Disclaimer: This guide provides general diagnostic procedures for experienced technicians. Always consult the official Komatsu PC110-7 service manual and consider professional diagnosis for complex electrical issues. Improper repairs may cause additional damage or safety hazards.