What is Komatsu PC240LC-8 Fault Code E-6?

Fault Code E-6 on the Komatsu PC240LC-8 indicates a hydraulic oil temperature sensor malfunction or abnormal hydraulic oil temperature condition. This diagnostic trouble code is triggered when the Electronic Control Module (ECM) detects an irregular signal from the hydraulic oil temperature sensor or when the hydraulic oil temperature exceeds safe operating limits.

This code is critical for the PC240LC-8's performance because the hydraulic system operates within strict temperature parameters. Excessive heat or sensor failure can lead to reduced hydraulic efficiency, component wear, and potential system damage. The ECM monitors this sensor continuously to protect pumps, motors, and valve components from thermal degradation, which is especially important in used excavators where cumulative operating hours increase vulnerability to heat-related failures.

Common Symptoms

• Hydraulic oil temperature warning light illuminates on the instrument panel
• Noticeable reduction in hydraulic response speed or sluggish boom/arm/bucket movements
• Derate mode activation, limiting engine RPM and hydraulic performance
• Unusual noise from the hydraulic pump during operation, indicating potential overheating
• Intermittent code appearance during heavy workloads or high ambient temperatures

Potential Causes

The most common technical causes for E-6 on used PC240LC-8 excavators include:

• Hydraulic oil temperature sensor failure due to internal element degradation (common after 8,000+ operating hours)
• Damaged or corroded wiring harness connections at the sensor plug, particularly where the harness routes near the hydraulic tank
• Actual hydraulic oil overheating caused by low oil levels, contaminated oil, or failing hydraulic cooler
• ECM voltage supply issues to the temperature sensor circuit (typically 5-volt reference signal problems)
• Worn hydraulic pump or relief valve issues causing excessive heat generation in older machines
• Clogged hydraulic oil cooler fins reducing heat dissipation efficiency

How to Troubleshoot and Fix Code E-6

Step 1: Initial Inspection Using Komatsu diagnostic software (KOMTRAX or compatible scanner), retrieve active and stored codes. Check actual hydraulic oil temperature readings versus sensor voltage output. Physically inspect the hydraulic oil temperature sensor located on the hydraulic tank for visible damage, corrosion, or oil leaks.

Step 2: Electrical Testing Disconnect the sensor wiring harness connector and use a digital multimeter to check sensor resistance (typical specification: 200-300 ohms at 20°C). Verify the ECM reference voltage at the harness connector (should read approximately 5 volts). Inspect connector pins for corrosion, bent terminals, or moisture intrusion—common issues in used excavators.

Step 3: Harness and Ground Verification Trace the sensor wiring harness from the sensor to the ECM, checking for abrasion points, especially where the harness contacts frame components or hydraulic lines. Test ground circuit continuity (should be less than 1 ohm resistance). On used machines, pay particular attention to harness wear near articulation points.

Step 4: Component Replacement or Repair If sensor resistance is out of specification, replace the hydraulic oil temperature sensor with genuine Komatsu parts. If wiring is damaged, repair using proper gauge wire and weatherproof connectors. Clear codes and monitor during a 30-minute operating cycle under load.

Critical for Used Excavators: Before replacing the sensor, verify actual hydraulic oil condition and temperature. Change hydraulic oil and filters if contaminated, and clean the hydraulic cooler thoroughly—often resolving false codes caused by actual overheating conditions rather than sensor failure.

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Disclaimer: This guide provides general troubleshooting information. Always consult the Komatsu PC240LC-8 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or create safety hazards.