Komatsu PC450-6 Fault Code E231: Complete Diagnostic Guide

What is Komatsu PC450-6 Fault Code E231?

Fault Code E231 indicates a malfunction in the hydraulic pump solenoid valve circuit, specifically detecting an abnormal electrical signal or open/short circuit in the pump control system. This code is generated when the machine's Electronic Control Module (ECM) detects voltage irregularities outside the normal operating range (typically 0.5-4.5V) in the proportional solenoid valve that regulates main hydraulic pump displacement.

This fault is critical for the PC450-6 because the pump solenoid valve directly controls hydraulic flow and pressure, which affects all machine functions including boom, arm, bucket, and swing operations. When this circuit fails, the excavator may enter a protective derate mode to prevent damage to the hydraulic system.

Common Symptoms

When Code E231 is active, operators typically experience:

• Reduced hydraulic power across all functions, with noticeably slower cycle times
• Intermittent or complete loss of hydraulic response, particularly during combined operations
• Warning light illumination on the monitor panel with possible audible alarm
• Engine running normally but hydraulic functions operating at significantly reduced capacity
• Erratic pump response where hydraulic power fluctuates unpredictably during operation

Potential Causes

The most common technical causes for E231 on used PC450-6 excavators include:

• Damaged wiring harness near the main pump area, where vibration and heat cause insulation breakdown
• Corroded or loose connector pins at the pump solenoid valve plug (common after 5,000+ hours)
• Failed proportional solenoid valve due to internal coil breakdown or contamination
• ECM internal circuit failure affecting the solenoid driver output
• Hydraulic oil contamination causing solenoid valve sticking or mechanical binding
• Voltage supply issues from the main power harness or ground connections

How to Troubleshoot and Fix Code E231

Step 1: Visual Inspection Begin by inspecting the pump solenoid valve connector located on the main hydraulic pump. Check for oil contamination, corrosion, bent pins, or moisture intrusion. On used excavators, this connector frequently suffers from environmental damage. Clean contacts with electrical contact cleaner and ensure proper seating.

Step 2: Electrical Testing Using a digital multimeter, measure resistance across the solenoid valve coil terminals (disconnect connector first). Normal resistance should be 3-6 ohms. Check for voltage supply at the harness connector with ignition on—should read approximately 12V. Test for shorts to ground on both signal wires.

Step 3: Harness Continuity Check Trace the wiring harness from the pump to the ECM, checking for rub points against the frame, particularly where the harness passes near the swing motor and along the main frame rail. These are known wear points on PC450-6 models. Repair any damaged insulation with heat-shrink tubing and protective loom.

Step 4: Solenoid Valve Replacement If electrical tests confirm solenoid failure, replace the proportional solenoid valve (Komatsu part number 702-21-55901 or equivalent). Before installation, flush the pump area and verify hydraulic oil cleanliness meets ISO 4406 standards.

Step 5: ECM Verification If all external components test normally, the ECM may require professional diagnosis using Komatsu diagnostic software (KOMTRAX or equivalent). This requires dealer-level equipment to test internal driver circuits.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific serial number and consider professional assistance for complex electrical diagnostics or hydraulic system repairs.