Komatsu PC100-6 Fault Code E206: Complete Diagnostic Guide

What is Komatsu PC100-6 Fault Code E206?

Fault Code E206 on the Komatsu PC100-6 indicates a malfunction in the hydraulic oil temperature sensor circuit. This code triggers when the engine control module (ECM) detects abnormal voltage readings from the temperature sensor monitoring hydraulic fluid temperature.

The hydraulic oil temperature sensor plays a critical role in the PC100-6's operational safety system. It prevents hydraulic system damage by monitoring oil temperature and alerting operators when thermal limits are exceeded. When this sensor circuit fails, the ECM cannot accurately protect the hydraulic system from overheating, potentially leading to seal degradation, reduced hydraulic efficiency, and catastrophic component failure.

Common Symptoms

When E206 is active, operators typically experience:

• Warning light illumination on the instrument cluster (typically orange/amber hydraulic temperature indicator)
• Hydraulic system performance degradation, including slower cycle times or reduced lifting capacity
• Audible alarm from the cab when the code first triggers
• ECM may enter derate mode, limiting engine RPM to protect the hydraulic system
• Intermittent activation during cold starts that clears after warm-up (indicates marginal sensor or wiring)

Potential Causes

The most common technical causes for E206 on used PC100-6 excavators include:

• Sensor failure due to internal resistance drift (common after 5,000+ operating hours)
• Corroded or damaged wiring connectors at the sensor location near the hydraulic tank
• Harness chafing where the sensor wire runs along the main pump mounting bracket (known wear point on this model)
• Failed sensor ground connection causing voltage reference errors
• Contaminated hydraulic oil creating deposits on the sensor probe element
• ECM internal fault (rare, but possible on machines with 10+ years of service)

How to Troubleshoot and Fix Code E206

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the left side of the hydraulic tank. Inspect the connector for corrosion, oil contamination, or damaged pins. On used excavators, check the entire wiring harness from sensor to ECM for rubbing points, especially where it passes near the swing motor mounting.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. At 20°C (68°F), resistance should read approximately 2,000-3,000 ohms (consult service manual for exact specifications). Check supply voltage at the connector with ignition on—should read 5V reference from ECM.

Step 3: Circuit Continuity Test wire continuity from sensor connector to ECM pins. Measure resistance (should be <5 ohms). Check for shorts to ground on both signal and reference wires. Inspect connector terminals for "push-back" or looseness.

Step 4: Sensor Replacement If sensor resistance is out of specification or wiring tests pass, replace the temperature sensor (Komatsu part #7861-93-3320 or equivalent). Always use dielectric grease on connectors during reassembly.

Step 5: Code Clearing and Verification After repairs, use Komatsu diagnostic software or a compatible scan tool to clear the fault code. Operate the machine through a complete work cycle and monitor for code recurrence.

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Disclaimer: This guide provides general diagnostic procedures. Always consult the official Komatsu PC100-6 service manual and consider professional technician assistance for complex electrical diagnostics or if you lack proper diagnostic equipment.