Komatsu PC70-8 Fault Code E-11: Complete Diagnostic Guide

What is Komatsu PC70-8 Fault Code E-11?

Fault Code E-11 on the Komatsu PC70-8 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal temperature reading detected by the Engine Control Module (ECM). This code specifically relates to the coolant temperature sensor failing to provide accurate data or experiencing an electrical circuit fault.

The coolant temperature sensor plays a critical role in the PC70-8's engine management system. It monitors engine operating temperature and sends voltage signals to the ECM, which adjusts fuel injection timing, idle speed, and activates cooling fan operation. When this sensor fails or its circuit is compromised, the engine cannot optimize performance, potentially leading to overheating, poor fuel economy, or engine protection mode activation.

Common Symptoms

When Code E-11 is active on your Komatsu PC70-8, operators typically experience:

• Warning light illumination on the instrument panel, often accompanied by an audible alarm
• Engine derate mode where power output is significantly reduced to prevent damage
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Hard starting conditions, especially in cold weather, due to incorrect fuel mapping
• Cooling fan running continuously at high speed, even when engine is cold

Potential Causes

The most common technical reasons for E-11 appearing on used PC70-8 excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal stress
• Damaged wiring harness near the sensor connector, particularly where harness routes near hot exhaust components or sharp edges
• Corroded or loose electrical connectors at the sensor or ECM terminals—extremely common in machines exposed to moisture
• Short circuit or open circuit in the sensor wiring between sensor and ECM
• ECM internal fault (rare, but possible in high-hour machines)
• Low coolant levels causing sensor exposure and false readings

How to Troubleshoot and Fix Code E-11

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, and verify adequate coolant level. Examine the wiring harness for abrasion, melting, or damage at known rub points along the engine valley.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. 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 pins, checking for opens or shorts to ground.

Step 3: Connector Inspection On used excavators, carefully inspect connector terminals for corrosion, bent pins, or moisture intrusion. Clean connections with electrical contact cleaner and apply dielectric grease. Check connector locking mechanisms—vibration often causes intermittent connections in older machines.

Step 4: Sensor Replacement and Verification If testing confirms sensor failure, replace with a genuine Komatsu coolant temperature sensor. After installation, clear codes using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then monitor for code recurrence during a complete heat cycle.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC70-8 service manual and consider professional assistance for complex electrical diagnostics or if you're unfamiliar with heavy equipment repair procedures.