Komatsu PC138US-8 Fault Code DHSGMA: Meaning and Fix Guide

What is Komatsu PC138US-8 Fault Code DHSGMA?

Fault Code DHSGMA on the Komatsu PC138US-8 indicates a communication error or malfunction in 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 abnormal voltage signals or loss of communication from the hydraulic pressure sensor that monitors pump output.

This fault is critical for the PC138US-8 because the hydraulic pressure sensor directly influences machine performance and fuel efficiency. The ECM uses this data to optimize pump flow and prevent over-pressurization that could damage seals, hoses, or the main hydraulic pump. When this code is active, the machine may enter a derated mode to protect the hydraulic system from potential damage.

Common Symptoms

When fault code DHSGMA is active, operators typically experience:

• Warning light illumination on the instrument panel with possible audible alarm
• Reduced hydraulic power or sluggish boom/arm/bucket response during operation
• Intermittent loss of auxiliary hydraulic functions (breaker or grapple circuits)
• Engine derating to limit pump demand, reducing overall machine productivity
• Erratic gauge readings for hydraulic system pressure on the monitor display

Potential Causes

The most common technical causes for DHSGMA on used PC138US-8 excavators include:

• Failed hydraulic pressure sensor due to internal component degradation or contamination exposure
• Damaged wiring harness near the main pump area where cables rub against frame members during swing operations
• Corroded or loose electrical connectors at the sensor plug, especially on machines operated in wet or marine environments
• ECM software glitches requiring calibration updates or memory reset
• Voltage supply issues from the machine's electrical system (low battery voltage or alternator problems)
• Hydraulic contamination causing sensor membrane failure or blocked pressure ports

How to Troubleshoot and Fix Code DHSGMA

Step 1: Visual Inspection Begin by inspecting the hydraulic pressure sensor located on the main pump assembly. Check for physical damage, oil contamination on the connector, or corrosion on pins. On used excavators, examine the wiring harness routing from the sensor to the ECM, looking for chafing points where cables contact metal surfaces during machine movement.

Step 2: Electrical Testing Using a digital multimeter, perform voltage and resistance checks. With ignition on (engine off), verify the sensor receives proper supply voltage (typically 5V reference). Check resistance values across sensor terminals according to Komatsu specifications (usually 200-400 ohms at room temperature). Test harness continuity from sensor connector to ECM pins to identify open circuits.

Step 3: Sensor Signal Verification Connect Komatsu diagnostic software (KOMTRAX Plus or equivalent) to monitor live sensor data. Start the engine and observe pressure readings during idle and under load. Erratic values or flat-line signals indicate sensor failure. For used machines, remove the sensor and inspect the pressure port for hydraulic debris or metal shavings that could block accurate readings.

Step 4: Component Replacement and Calibration If testing confirms sensor failure, replace with a genuine Komatsu pressure sensor (part-specific to PC138US-8). After installation, clear fault codes and perform ECM calibration using diagnostic software to ensure proper signal recognition. Check for code recurrence after operating the machine through full hydraulic cycles.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC138US-8 service manual and consider professional diagnostic assistance for complex electrical or hydraulic system repairs. Improper repairs may void warranties or create safety hazards.