What is Komatsu PC110-8M0 Fault Code E-31?

Fault Code E-31 on the Komatsu PC110-8M0 indicates a malfunction in the pump solenoid valve circuit for the hydraulic system. Specifically, this code signals that the Engine Control Module (ECM) has detected an abnormal electrical signal or current flow in the solenoid valve that regulates hydraulic pump output.

This fault directly affects the machine's ability to properly modulate hydraulic flow based on operational demands. The Komatsu PC110-8M0 relies on precise solenoid valve control to match pump displacement with load requirements, optimizing fuel efficiency and hydraulic response. When E-31 appears, the excavator may revert to a failsafe mode that compromises productivity and can accelerate component wear if left unresolved.

Common Symptoms

When fault code E-31 is active, operators typically experience:

• Erratic hydraulic power with inconsistent boom, arm, or bucket response during cycles
• Reduced digging force or sluggish hydraulic functions, particularly under load
• Warning lamp illumination on the instrument panel (typically amber or red hydraulic system alert)
• Intermittent loss of hydraulic pressure that may resolve temporarily then return
• Increased engine RPM without corresponding hydraulic output as the system attempts compensation

Potential Causes

The most common technical causes for E-31 on used PC110-8M0 excavators include:

• Pump solenoid valve coil failure due to overheating or internal short circuits (common after 5,000+ operating hours)
• Wiring harness damage at known rub points near the hydraulic pump mounting area where vibration causes insulation wear
• Corroded or loose connector pins at the solenoid valve harness connection, particularly in machines operating in wet or coastal environments
• ECM internal circuit issues affecting solenoid driver outputs (less common but possible in high-hour machines)
• Voltage supply problems from the main power harness or grounding issues at the pump assembly mounting points

How to Troubleshoot and Fix Code E-31

Step 1: Visual Inspection and Connector Check Begin by disconnecting the battery ground. Locate the pump solenoid valve mounted on the hydraulic pump assembly. Inspect the electrical connector for corrosion, bent pins, or moisture intrusion—common in used excavators. Clean contacts with electrical contact cleaner and check for physical harness damage along routing paths.

Step 2: Electrical Testing with Multimeter Using a digital multimeter, measure solenoid coil resistance at the valve connector (disconnected). Typical specification is 3-7 ohms; consult the service manual for exact values. Check for continuity to ground—there should be infinite resistance. With ignition on (engine off), verify the solenoid receives proper voltage supply (typically 12-24V depending on system) from the ECM during activation.

Step 3: Harness and Ground Verification Trace the wiring harness from solenoid to ECM, checking for chafing at frame contact points and zip-tie locations. On used machines, inspect grounding points at the pump mounting bolts—remove, clean with a wire brush, and apply dielectric grease before reinstalling. Use your diagnostic software (Komatsu KOMTRAX or KTCM) to monitor real-time solenoid current draw during operation.

Step 4: Component Replacement If resistance values are out of specification or voltage tests confirm ECM output is correct but the solenoid doesn't respond, replace the pump solenoid valve assembly. For persistent codes after solenoid replacement, ECM driver circuit failure may require controller replacement or professional ECM repair.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific serial number and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional damage or safety hazards.