Komatsu PC220-10 Fault Code DHSHMA: Complete Diagnostic Guide

What is Komatsu PC220-10 Fault Code DHSHMA?

Fault Code DHSHMA indicates a Hydraulic System High Pressure Abnormality in the main pump delivery circuit of the Komatsu PC220-10 excavator. This code is triggered when the Electronic Control Unit (ECU) detects abnormal pressure readings from the main hydraulic pump pressure sensor, typically when system pressure exceeds programmed thresholds or shows erratic fluctuations during operation.

This fault is critical because the PC220-10's Komtrax monitoring system relies on accurate hydraulic pressure data to optimize fuel efficiency and prevent catastrophic pump damage. In used excavators, this code often signals developing issues in the variable displacement pump control system or degraded sensors that can lead to reduced lifting capacity and expensive hydraulic system failures if left unaddressed.

Common Symptoms

When DHSHMA is active on your Komatsu PC220-10, operators typically experience:

• Yellow caution lamp illuminated on the monitor panel with accompanying audible warning
• Noticeable reduction in boom and arm speed during combined hydraulic functions
• Intermittent power loss when operating under heavy loads or during simultaneous multi-function operation
• Abnormal hydraulic oil temperature increases beyond normal operating range (above 80°C)
• Machine may enter derate mode, limiting engine RPM to approximately 1,800 to protect hydraulic components

Potential Causes

The most common technical causes for DHSHMA in used PC220-10 excavators include:

• Main pump pressure sensor failure (part #: 7861-93-1650) due to internal diaphragm degradation common after 6,000+ operating hours
• Contaminated or incorrect hydraulic oil viscosity causing pressure spikes during cold starts
• Worn main relief valve allowing pressure fluctuations that trigger false codes
• Corroded or damaged wiring harness at the sensor connector located near the left-side pump housing—a known wear point where harness rubs against frame
• Faulty pump regulator solenoid causing erratic swashplate angle adjustments
• ECU calibration drift in older machines requiring software update or replacement

How to Troubleshoot and Fix Code DHSHMA

Step 1: Connect Diagnostic Software Use Komatsu KOWA diagnostic software or compatible scan tool to read live data. Monitor main pump pressure readings at idle (should be 25-35 bar) and under load (280-350 bar maximum). Erratic readings point to sensor issues; consistent over-pressure indicates mechanical failure.

Step 2: Inspect Pressure Sensor and Harness Locate the main pump pressure sensor on the pump delivery manifold. Check connector for corrosion, oil contamination, or bent pins. Using a digital multimeter, verify sensor resistance (typically 250-350 ohms at 20°C). Inspect wiring harness along the frame rail for chafing—a common issue in used machines with 5,000+ hours.

Step 3: Test Hydraulic System Mechanically Install a calibrated hydraulic pressure gauge at the test port. Compare readings against sensor data. If gauge shows normal pressure but sensor reads high, replace the sensor. If both show excessive pressure, inspect the main relief valve for debris or wear, and check hydraulic oil condition (contamination accelerates valve wear).

Step 4: Verify Pump Regulator Function Test the pump regulator solenoid (part #: 702-16-01583) by commanding it with diagnostic software. Listen for audible click and measure voltage (should be 12V). Check oil filter condition—clogged filters cause backpressure that affects regulator response.

For used excavators, always inspect hydraulic oil cooler for blockages and verify oil meets Komatsu specifications before replacing expensive components.

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Disclaimer: This guide provides general diagnostic procedures. Always consult the official Komatsu PC220-10 service manual and consider professional technician evaluation for complex hydraulic system repairs. Improper diagnosis can lead to component damage and safety hazards.