What is Komatsu PC110-8M0 Fault Code E-27?

Fault Code E-27 on the Komatsu PC110-8M0 indicates a hydraulic pump solenoid circuit malfunction, specifically related to the main pump control valve electrical system. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage or resistance in the hydraulic pump's proportional solenoid circuit, which directly regulates the pump's displacement and flow output.

This code is critical for the PC110-8M0 because the hydraulic pump solenoid controls engine-to-pump matching, ensuring optimal fuel efficiency and hydraulic performance. When E-27 appears, the machine typically enters a derate mode that limits hydraulic flow to prevent damage, significantly reducing digging force, swing speed, and overall productivity. For used excavators, this fault often stems from age-related electrical degradation rather than catastrophic component failure.

Common Symptoms

When Code E-27 is active on your Komatsu PC110-8M0, operators typically experience:

• Reduced hydraulic power across all functions (boom, arm, bucket movements are noticeably slower)
• Warning light illuminated on the instrument panel, often accompanied by an audible alarm
• Engine runs normally but excavator operates in "limp mode" with limited performance
• Intermittent loss of power that may temporarily resolve after restarting, then return under load
• Increased engine RPM without corresponding increase in hydraulic response

Potential Causes

The most common technical reasons for E-27 on used PC110-8M0 excavators include:

• Solenoid valve coil failure due to internal short circuit or open winding (resistance out of specification: should be 18-22 ohms)
• Wiring harness damage at the pump mounting area where vibration causes insulation wear and exposed conductors
• Corroded connectors on the solenoid plug, particularly the 3-pin connector near the hydraulic pump (common water intrusion point)
• ECM supply voltage issues – the control module should provide 12V PWM signal; degraded grounds cause erratic readings
• Previous repair attempts where aftermarket solenoids with incorrect specifications were installed

How to Troubleshoot and Fix Code E-27

Step 1: Visual Inspection and Connector Check Begin by disconnecting the battery negative terminal for safety. Locate the hydraulic pump solenoid on the main pump body (driver's side of engine). Inspect the 3-pin connector for corrosion, pushed-back pins, or moisture intrusion. On used excavators, this connector frequently shows green corrosion—clean with electrical contact cleaner and dielectric grease.

Step 2: Solenoid Resistance Testing Using a digital multimeter, disconnect the solenoid connector and measure resistance across the solenoid terminals. The specification for the PC110-8M0 is 18-22 ohms at 20°C. If resistance reads infinite (open circuit) or below 10 ohms (short circuit), the solenoid coil has failed and requires replacement (Komatsu part number 702-21-57400).

Step 3: Wiring Harness and Voltage Supply Verification Trace the wiring from the ECM (located under the operator cab) to the pump solenoid. Check for harness chafing at the engine mount bracket—a known wear point on PC110 models. With ignition on (engine off), measure voltage at the harness connector: you should see battery voltage (12-14V) when commanded by diagnostic software like Komatsu KOMTRAX or aftermarket tools (Jaltest, OEM scan tools). Check for clean ground continuity (less than 0.5 ohms to chassis ground).

Step 4: ECM Signal Testing (Advanced) If solenoid and wiring test good, connect diagnostic software to verify the ECM is sending proper PWM signals (pulse-width modulation). The duty cycle should vary with hydraulic demand (typically 10-90%). A fixed signal or no signal indicates potential ECM programming issues or internal ECM failure, requiring dealer-level diagnostics.

Critical for Used Excavators: Before replacing expensive components, thoroughly inspect all connector seals and harness routing. Machines with 3,000+ hours often have multiple previous repairs that created new failure points. Apply dielectric grease to all reconnected plugs to prevent future corrosion.

---

Disclaimer: This guide provides general troubleshooting information. Hydraulic systems operate under extreme pressure. Always consult the official Komatsu service manual for your specific serial number and seek qualified technician assistance for complex electrical diagnostics or hydraulic component replacement.