Komatsu PC210-10 Fault Code DHS3MA: Complete Diagnostic Guide

What is Komatsu PC210-10 Fault Code DHS3MA?

Fault Code DHS3MA indicates a communication error between the Machine Control Unit (MCU) and the Hydraulic Management Computer (HMC) on the Komatsu PC210-10 excavator. This diagnostic trouble code specifically signals that the Controller Area Network (CAN) bus communication line has detected an abnormal signal or complete loss of data transmission between these two critical control modules.

The PC210-10 relies on seamless communication between the MCU and HMC to coordinate engine performance with hydraulic demand, manage fuel efficiency through the KOMTRAX Plus system, and maintain optimal working modes. When this communication fails, the machine cannot properly balance power output with hydraulic functions, directly impacting productivity and potentially causing component damage from uncoordinated system operation.

This fault is particularly critical because the HMC governs main pump output, swing priority, and attachment flow control—all dependent on real-time data from the MCU. Without proper communication, the excavator defaults to protective limp mode.

Common Symptoms

• Monitor panel displays "HYD SYSTEM ERROR" or shows both engine and hydraulic warning icons simultaneously
• Significant loss of hydraulic power across all functions, with boom and bucket movements feeling sluggish or unresponsive
• Engine fails to respond to increased hydraulic demand, causing stalling under load that wouldn't normally challenge the machine
• Intermittent or complete loss of working mode selection (PWR, STD, ECO modes become non-functional or revert unexpectedly)
• KOMTRAX system loses connectivity or displays incomplete machine data

Potential Causes

CAN bus wiring harness damage is the primary culprit in used PC210-10 excavators, especially at the harness routing point beneath the operator's cab where vibration and house rotation cause insulation wear. The factory harness routing creates a known rub point against the cab mounting bracket.

Corroded connector terminals at either the MCU connector (located in the electrical component box under the cab) or HMC connector (mounted on the right side of the main pump) frequently cause intermittent communication failures, particularly in machines operating in wet or coastal environments.

HMC internal circuit board failure occurs in higher-hour machines (typically 8,000+ hours) due to heat exposure and voltage fluctuations. The PC210-10 HMC (part number 7835-46-1004) has known capacitor degradation issues.

MCU software corruption or version mismatch following previous electrical system repairs can prevent proper protocol communication between controllers.

Low system voltage or poor grounding at the main negative bus bar creates erratic CAN bus signal levels, especially evident during cold starts.

How to Troubleshoot and Fix Code DHS3MA

Step 1: Visual Inspection of CAN Bus Harness Start by examining the CAN-H (white/blue) and CAN-L (white/orange) wires running from the MCU to the HMC. On used excavators, inspect the harness where it exits the electrical component box and routes along the engine compartment bulkhead. Look for abraded insulation, particularly at metal contact points. Use a digital multimeter set to continuity mode to verify no shorts between the two CAN wires (should show open circuit/infinite resistance).

Step 2: Connector Terminal Inspection Disconnect the 32-pin MCU connector and 20-pin HMC connector. Inspect for green corrosion (copper oxide), bent pins, or moisture intrusion. Clean terminals with electrical contact cleaner and a fine brass brush. Measure pin-to-pin resistance between terminals 17 (CAN-H) and 18 (CAN-L) at both connectors—should read approximately 60 ohms with both modules disconnected (this is the termination resistance).

Step 3: Voltage and Ground Verification With the ignition key ON (engine off), measure voltage at the HMC power supply pin (typically terminal 1)—should read battery voltage (12-14V). Check ground integrity by measuring voltage drop between the HMC mounting bolts and battery negative—should be less than 0.1V. Poor grounding is common in used machines where paint buildup or corrosion affects controller chassis grounds.

Step 4: CAN Bus Signal Testing Using Komatsu VHMS (Vehicle Health Monitoring System) diagnostic software or an aftermarket tool like Jaltest with Komatsu coverage, monitor live CAN bus traffic. The software should show active messaging between MCU and HMC at the standard 250 kbps rate. If no traffic appears, measure voltage on CAN-H (should fluctuate 2.5-3.5V) and CAN-L (should fluctuate 1.5-2.5V) during key-on. Static voltage readings indicate a failed controller.

Step 5: Component Isolation If wiring and voltage checks pass, disconnect the HMC connector and clear codes. If DHS3MA disappears, the HMC likely has internal failure. If the code remains, suspect MCU failure or software corruption. For used excavators over 10,000 hours, requesting ECU software verification and update through Komatsu dealer service often resolves intermittent communication faults caused by outdated firmware.

Critical for Used Equipment: Before replacing expensive controllers (HMC ~$1,800, MCU ~$2,400), thoroughly inspect all chassis ground points, especially the engine-to-frame ground strap and battery negative cable connections. Corrosion at these points causes 40% of CAN communication faults in excavators beyond 5 years old.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Komatsu PC210-10 Service Manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs to CAN bus systems can cause cascading controller failures.