Komatsu PC200LC-7 Fault Code E-6: Comprehensive Diagnostic Guide

What is Komatsu PC200LC-7 Fault Code E-6?

Fault Code E-6 on the Komatsu PC200LC-7 indicates a malfunction in the hydraulic oil temperature sensor circuit. This code is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal from the temperature sensor monitoring the hydraulic oil in the system.

The hydraulic oil temperature sensor plays a critical role in protecting the hydraulic system by monitoring operating temperatures. When oil becomes too hot, it loses viscosity and can cause severe damage to pumps, motors, and seals. On the PC200LC-7, this sensor sends continuous analog voltage signals to the ECM, which uses this data to activate warning systems and prevent thermal damage. A faulty sensor or circuit can lead to inaccurate temperature readings, potentially causing overheating damage or unnecessary machine shutdowns.

Common Symptoms

• Hydraulic temperature warning light illuminated on the instrument panel
• Intermittent loss of hydraulic power or reduced machine performance
• Erratic temperature gauge readings that don't correspond with actual operating conditions
• Machine may enter derate mode or activate safety shutdowns even when hydraulic oil is cool
• Audible warning alarms sounding without visible overheating conditions

Potential Causes

The E-6 code on used PC200LC-7 excavators typically stems from age-related deterioration:

• Sensor failure due to prolonged heat exposure and thermal cycling over years of operation
• Corroded or loose electrical connections at the sensor harness connector near the hydraulic tank
• Damaged wiring harness caused by rubbing against the tank mounting bracket (a known wear point on this model)
• Short circuit or open circuit in the sensor wiring due to insulation breakdown
• ECM malfunction (rare, but possible in high-hour machines with electrical system degradation)
• Contamination or moisture intrusion in the sensor connector causing intermittent signals

How to Troubleshoot and Fix Code E-6

Step 1: Visual Inspection Locate the hydraulic oil temperature sensor on the left side of the hydraulic tank. Inspect the wiring harness for visible damage, particularly where it routes near metal edges. Check the connector for corrosion, bent pins, or oil contamination. On used excavators, this connector often shows green corrosion—clean with electrical contact cleaner and apply dielectric grease.

Step 2: Electrical Testing Disconnect the sensor and use a digital multimeter to check resistance. At room temperature (20°C/68°F), resistance should read approximately 2.4-2.7 kΩ. As temperature increases, resistance decreases. Compare readings with Komatsu specifications. Also check for continuity in the wiring from sensor to ECM connector (Pin locations specified in service manual).

Step 3: Signal Voltage Check With the sensor connected and ignition on (engine off), backprobe the signal wire at the sensor connector. You should see approximately 5V reference voltage from the ECM. Start the engine and monitor voltage as oil warms—it should decrease gradually (typically 4.5V cold to 1.5V hot). Erratic voltage indicates sensor failure.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu part (Part #7861-93-3320 or equivalent). When installing, ensure the O-ring is properly seated and apply anti-seize to threads. After replacement, use Komatsu diagnostic software (KOMTRAX) or a compatible scan tool to clear codes and verify proper operation.

Critical for Used Machines: Before purchasing expensive components, thoroughly inspect all harness routing and connectors. Many E-6 codes on older PC200LC-7s result from simple wiring issues rather than sensor failure itself.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number. If you're unfamiliar with electrical diagnostics or hydraulic systems, contact a certified Komatsu technician to prevent injury or further damage.