What is Komatsu PC100-6 Fault Code E-8?

Komatsu PC100-6 Fault Code E-8 indicates a malfunction in the engine controller (ECM) communication system or a critical sensor circuit failure within the hydraulic pump control system. This code specifically points to abnormal voltage readings or signal interruptions between the ECM and the pump flow control solenoid or related sensors that regulate hydraulic output based on engine load.

This fault is critical for the PC100-6 because it directly affects the machine's ability to match hydraulic pump output with engine performance. When E-8 is active, the excavator may enter a protective derate mode, limiting both engine power and hydraulic flow to prevent damage. For used machines, this code often stems from age-related wiring degradation rather than component failure.

Common Symptoms

• Engine warning light illuminated on the dashboard, sometimes accompanied by intermittent buzzer alerts
• Noticeable loss of hydraulic power during simultaneous multi-function operations (e.g., boom lift with swing)
• Engine RPM fluctuation or inability to maintain consistent operating speed under load
• Hydraulic pump producing unusual whining or cavitation noises during operation
• Machine entering limp mode with limited swing speed and reduced digging force

Potential Causes

The most common causes for E-8 on used PC100-6 excavators include:

• Corroded or loose connector pins at the pump control solenoid (typically located on the main hydraulic pump body)
• Wiring harness chafing where the engine harness passes near the swing motor mount—a known wear point on this model
• Failed pump flow control solenoid due to internal coil breakdown or contaminated hydraulic oil entering the electrical connector
• ECM ground circuit failure caused by corrosion on chassis ground points near the battery box
• Damaged engine speed sensor providing erratic signals to the ECM, disrupting pump control calculations

How to Troubleshoot and Fix Code E-8

Step 1: Visual Inspection Begin by inspecting the pump control solenoid connector for oil contamination, corrosion, or bent pins. On used PC100-6 machines, check the main engine harness routing near the swing bearing for visible abrasion or wire exposure—this is a documented friction point.

Step 2: Electrical Testing Using a digital multimeter, measure resistance across the pump solenoid terminals (should read 18-25 ohms at 20°C). Check supply voltage at the solenoid connector with ignition on (should read 12V±0.5V). Test ECM ground circuits for resistance below 1 ohm.

Step 3: Connector Service and Monitoring Clean all connectors with electrical contact cleaner and apply dielectric grease. For used excavators, replace any corroded terminals rather than attempting repairs. Clear the code using Komatsu diagnostic software (PCMS or compatible tool) and monitor during a 30-minute operational test under load.

Professional Consultation Disclaimer: While these diagnostic steps address common E-8 causes, complex ECM programming issues or internal hydraulic pump failures require factory-trained technicians with OEM diagnostic equipment.