Komatsu PC800-7 Fault Code E115: Complete Diagnostic Guide

What is Komatsu PC800-7 Fault Code E115?

Fault Code E115 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 sensor sending irregular voltage signals outside the manufacturer's specified parameters, typically between 0.5-4.5 volts.

The coolant temperature sensor plays a critical role in the PC800-7's SAA6D140E-5 engine management system. It directly influences fuel injection timing, engine protection protocols, and hydraulic system performance. When this sensor fails or provides inaccurate data, the ECM cannot properly regulate engine temperature, potentially leading to overheating, reduced power output, or premature component wear—particularly critical concerns in high-hour used excavators.

Common Symptoms

When Code E115 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel with possible audible alarm
• Hard starting or extended cranking time, especially in cold conditions
• Engine derate mode activated, limiting maximum RPM and hydraulic flow
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Black smoke from exhaust due to improper fuel mixture compensation
• Cooling fan running continuously at high speed regardless of actual engine temperature

Potential Causes

The most common technical causes for E115 in used PC800-7 excavators include:

• Coolant temperature sensor failure due to internal element degradation (common after 8,000+ operating hours)
• Corroded or loose connector pins at the sensor harness connection point
• Damaged wiring harness between sensor and ECM, particularly where harness routes near engine mounts (known rub point)
• Contaminated coolant causing sensor element coating or corrosion
• ECM internal circuit failure (less common, but possible in high-hour machines)
• Poor ground connection at sensor mounting location due to gasket deterioration

How to Troubleshoot and Fix Code E115

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block's coolant passage. Check the electrical connector for corrosion, bent pins, or moisture intrusion. On used excavators, examine the wiring harness routing for signs of chafing, especially where it contacts the engine block or frame rails.

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 harness continuity from sensor connector to ECM pins, checking for opens or shorts to ground.

Step 3: Live Data Analysis Connect Komatsu KOMTRAX diagnostic software or compatible scan tool. Monitor live coolant temperature readings while engine warms up. The reading should gradually increase from ambient to operating temperature (180-200°F). Erratic jumps or frozen values indicate sensor failure.

Step 4: Sensor Replacement and Verification If testing confirms sensor failure, replace with genuine Komatsu part (P/N 6732-81-3140 or equivalent). Apply thread sealant to prevent coolant leaks. For used machines, inspect the sensor mounting boss for corrosion and clean thoroughly before installation. Clear codes and perform a test cycle.

Critical for Used Equipment: Before replacing components, thoroughly clean all electrical connectors with contact cleaner and apply dielectric grease. Many E115 codes on older PC800-7 excavators resolve through connector maintenance alone, saving unnecessary parts replacement costs.

---

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number. Complex electrical diagnostics should be performed by qualified technicians with proper diagnostic equipment.