Komatsu PC220-10 Fault Code DHS8MA: Technical Guide

What is Komatsu PC220-10 Fault Code DHS8MA?

Fault code DHS8MA on the Komatsu PC220-10 indicates a communication error or abnormal signal from the hydraulic system's pressure sensor circuit, specifically related to the main pump delivery pressure monitoring system. This code triggers when the ECM (Engine Control Module) detects an out-of-range voltage signal or intermittent communication from the pressure sensor that monitors the hydraulic pump's output.

This fault is critical for the PC220-10 because the main pump pressure sensor provides real-time data to the machine's control system, allowing proper regulation of hydraulic flow, attachment speed, and fuel efficiency. When this sensor circuit fails, the excavator may enter a derate mode to prevent hydraulic system damage or inefficient operation.

Common Symptoms

When fault code DHS8MA is active, operators typically experience:

• Hydraulic performance derate – reduced boom, arm, or bucket speed even at full throttle
• Intermittent warning lamp illumination on the monitor panel, sometimes accompanied by audible alerts
• Erratic hydraulic response – inconsistent attachment movements or delayed reactions to joystick inputs
• Monitor display error messages specifically referencing hydraulic system anomalies
• Increased fuel consumption due to the ECM running in failsafe mode without accurate pressure feedback

Potential Causes

The most common technical causes for DHS8MA on used PC220-10 excavators include:

• Pressure sensor failure – internal sensor degradation from heat cycles and contamination exposure over thousands of operating hours
• Wiring harness damage – specifically at the sensor connector near the main pump, a known rub point where the harness contacts the engine mount bracket
• Corroded or loose connector pins at the sensor plug, especially on machines operating in wet or marine environments
• ECM voltage supply issues – damaged wiring between the ECM and sensor causing voltage drops below the 4.5V threshold
• Contaminated hydraulic oil causing sensor element fouling or deposits on the sensing diaphragm

How to Troubleshoot and Fix Code DHS8MA

Step 1: Visual Inspection Begin by locating the main pump pressure sensor on the left side of the hydraulic pump assembly. Inspect the sensor body for physical damage, oil leaks, or loose mounting. Check the wiring harness from the sensor to the ECM for abrasion, particularly where it passes near the engine mount – this is a common failure point on used machines.

Step 2: Electrical Testing Using a digital multimeter, check the sensor's voltage supply. With ignition on (engine off), measure voltage at the sensor connector – it should read approximately 5.0V (±0.5V) on the supply pin. Check ground continuity (should be less than 1 ohm resistance). If voltage is outside specification, trace the harness back to the ECM for damaged wiring.

Step 3: Sensor Signal Verification With the engine running, use Komatsu KOMTRAX or compatible diagnostic software to monitor real-time pressure values. Compare actual hydraulic pressure (measured with a mechanical gauge at the test port) against the sensor's reported values. A discrepancy greater than 10% indicates sensor failure. On used excavators, also check for intermittent signals by wiggling the harness – if the code resets or values fluctuate, replace the damaged harness section and apply protective loom covering.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu pressure sensor (Part# 7861-93-1651 or equivalent). Clean all connector pins with electrical contact cleaner and apply dielectric grease to prevent future corrosion – especially critical on older machines. After installation, clear the fault code using diagnostic software and perform a hydraulic function test under load to verify proper operation.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the Komatsu PC220-10 service manual for model-specific procedures. Complex electrical diagnostics should be performed by certified technicians with proper diagnostic equipment. Improper repairs may cause further damage or safety hazards.