Komatsu PC800SE-7 Fault Code E315: Complete Diagnostic Guide

What is Komatsu PC800SE-7 Fault Code E315?

Fault Code E315 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 or detecting temperatures outside the normal operating parameters for the Komatsu SAA6D140E-7 engine.

This fault is critical because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, control engine protection systems, and manage hydraulic oil temperature. Ignoring E315 can lead to engine overheating, reduced performance, or automatic derate mode activation to prevent catastrophic engine damage.

Common Symptoms

When Code E315 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel with possible audible alarm
• Engine derate or power reduction mode, limiting machine performance to protect components
• Difficulty starting in cold conditions or excessive white smoke during warm-up
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Inaccurate temperature readings displayed on the operator monitor (showing extremely high or low values)

Potential Causes

The most common technical reasons for E315 on used PC800SE-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal short/open circuit
• Damaged or corroded wiring harness connections at the sensor plug (common wear point near engine block)
• Corroded pins or moisture intrusion in the sensor connector, especially on machines operating in wet environments
• Faulty ECM ground connections causing voltage reference issues
• Actual engine overheating due to cooling system failures (low coolant, failed thermostat, clogged radiator)
• Previous repair attempts using non-OEM sensors with incorrect resistance specifications

How to Troubleshoot and Fix Code E315

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block's coolant passage. Check for physical damage, coolant leaks around the sensor base, and examine the wiring harness for abrasion, cuts, or heat damage. On used excavators, pay special attention to harness routing near moving components or hot exhaust areas.

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

Step 3: Connector and Ground Verification Clean all connector pins with electrical contact cleaner and inspect for corrosion or bent terminals. Verify ECM ground connections are tight and free from corrosion—a common issue on older machines causing multiple sensor codes.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu coolant temperature sensor (Part #6754-81-6210 or equivalent). After installation, clear codes using Komatsu diagnostic software (KOMTRAX) and perform a test run to verify proper temperature readings.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific serial number and consider professional diagnosis for complex electrical issues or if you lack proper diagnostic equipment.