What is Komatsu PC160LC-7 Fault Code E-6?

Fault Code E-6 on the Komatsu PC160LC-7 indicates a hydraulic pump control system malfunction, specifically related to the engine-pump matching control circuit or pressure compensation valve circuit failure. This code triggers when the machine's Electronic Control Module (ECM) detects abnormal voltage signals or improper communication between the engine controller and the hydraulic pump's proportional solenoid valve.

This fault is critical because the PC160LC-7 relies on precise engine-pump matching to optimize fuel efficiency and hydraulic performance. When the ECM cannot properly regulate pump output based on engine load, you'll experience reduced productivity, excessive fuel consumption, and potential damage to hydraulic components. In used excavators, this code often signals deteriorating electrical connections or worn solenoid valves that have accumulated thousands of operating hours.

Common Symptoms

• Warning light illuminated on the instrument panel with active E-6 code display on the monitor
• Noticeable loss of hydraulic power during multi-function operations (swing and boom movements feel sluggish simultaneously)
• Erratic engine RPM fluctuations when engaging hydraulic functions under load
• Excessive hydraulic oil temperature due to improper pump displacement control
• Machine may enter derated mode, limiting maximum engine speed to protect components

Potential Causes

The most common causes of E-6 codes in used PC160LC-7 excavators include:

• Proportional solenoid valve failure on the main hydraulic pump (internal coil degradation after 6,000+ hours)
• Wiring harness damage between the ECM and pump solenoid—particularly at the routing point near the hydraulic tank where vibration causes insulation wear
• Corroded or loose connector pins at the pump solenoid harness (C-208 connector), especially on machines operated in wet or corrosive environments
• Voltage supply issues from the main power harness due to corroded ground connections at G-102 grounding point
• ECM calibration drift or internal relay failure (less common but documented in machines with 8,000+ operating hours)

How to Troubleshoot and Fix Code E-6

Step 1: Connect Diagnostic Software Use Komatsu KOMTRAX diagnostic software or compatible Komatsu PC Service Tool to retrieve live data. Monitor the proportional solenoid valve command signal (should vary 0-12V based on load) and actual current draw (typically 300-800mA).

Step 2: Inspect Electrical Connections Power off the machine and locate the proportional solenoid connector (C-208) on the main pump. Inspect for:

• Green corrosion on pins (clean with electrical contact cleaner)
• Bent or recessed pins preventing proper contact
• Harness chafing at the frame pass-through near the hydraulic reservoir—a known wear point on used PC160LC-7s

Step 3: Test Solenoid Resistance Disconnect the solenoid connector and measure resistance across the solenoid coil terminals using a digital multimeter. Specification is typically 10-14 ohms at 20°C. Values outside this range indicate coil failure requiring solenoid replacement (Komatsu P/N 702-21-55901).

Step 4: Verify Voltage Supply With ignition on (engine off), backprobe the harness connector and verify 12V supply voltage at the power pin. Check ground continuity to chassis ground—resistance should be less than 1 ohm. High resistance indicates corroded ground at G-102 mounting bolt behind the operator cab.

Step 5: Perform Solenoid Function Test If resistance and voltage are correct, use diagnostic software to manually activate the solenoid at varying percentages (25%, 50%, 75%, 100%). Listen for audible clicking and measure actual current draw. Inconsistent operation confirms internal valve sticking—common in excavators with contaminated hydraulic oil history.

Critical for Used Excavators: Before replacing the expensive proportional solenoid assembly, inspect the wiring harness routing for signs of previous repairs or zip-tie modifications that create new rub points. Many E-6 codes stem from intermittent shorts caused by harness movement rather than actual component failure.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC160LC-7 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or create safety hazards.