Komatsu PC220-8 Fault Code DHSAMA: Complete Diagnostic Guide

What is Komatsu PC220-8 Fault Code DHSAMA?

Fault Code DHSAMA on the Komatsu PC220-8 indicates a communication error between the Engine Controller (ECM) and the Hydraulic System Controller (HSC). This diagnostic trouble code specifically signals that the Controller Area Network (CAN) bus has detected an intermittent or complete loss of data transmission between these critical control modules.

This code is particularly important for the PC220-8 because this model relies on integrated electronic-hydraulic coordination to optimize fuel efficiency and hydraulic performance. When communication fails, the machine's ECM cannot properly regulate engine output based on hydraulic demand, leading to reduced operational efficiency and potential component stress. The CAN bus system on this excavator uses dual-wire twisted pair communication operating at specific voltage parameters, and any disruption compromises the entire machine management system.

Common Symptoms

When fault code DHSAMA is active, operators typically experience:

• Engine warning light illuminated on the monitor panel, often accompanied by a communication error message
• Reduced hydraulic response or sluggish boom/arm/bucket movements due to loss of load-sensing coordination
• Engine operating in fixed RPM mode rather than responding dynamically to hydraulic load demands
• Intermittent gauge failures on the monitor display, including inaccurate fuel level or hydraulic temperature readings
• Machine entering derate mode limiting engine power output to protect components during communication failures

Potential Causes

The most common technical causes for DHSAMA in used PC220-8 excavators include:

• Corroded or damaged CAN bus connectors at the ECM or HSC connection points (common wear point on machines with 4,000+ operating hours)
• Frayed or pinched wiring harness between the engine compartment and cab, particularly where harnesses pass through the swing bearing area
• Failed terminating resistors in the CAN network causing signal reflection and data corruption
• Water intrusion into the controller connectors due to deteriorated seals or improper storage
• Loose ground connections at either the ECM or HSC mounting points
• ECM or HSC internal failure, though less common than wiring issues in used equipment

How to Troubleshoot and Fix Code DHSAMA

Step 1: Visual Inspection of Harness and Connectors Begin by inspecting the main wiring harness running from the engine compartment to the operator's cab. On used PC220-8 excavators, pay special attention to harness routing near the swing bearing and hydraulic pump area where vibration and movement create friction points. Disconnect the CAN bus connectors at both the ECM (located on the right side of the engine) and the HSC (typically mounted under the operator's seat). Check for corrosion, bent pins, or moisture inside the connectors.

Step 2: Electrical Testing with Diagnostic Tools Using a digital multimeter, measure the resistance between the CAN-High and CAN-Low wires at the ECM connector with all controllers disconnected. You should read approximately 60 ohms, indicating proper terminating resistor function. Next, connect Komatsu KOMTRAX or compatible diagnostic software to verify real-time communication status. Check for voltage fluctuations on the CAN lines—they should maintain steady 2.5V differential during normal operation.

Step 3: Connector Cleaning and Harness Repair For used excavators, clean all CAN bus connectors with electrical contact cleaner and apply dielectric grease to prevent future corrosion. Inspect the twisted-pair wiring for any damage; if found, repair using proper shielded CAN-rated wire and heat-shrink connections. Verify all ground points are clean and torqued to specification (typically 10-12 ft-lbs for controller grounds).

Step 4: Component Replacement if Necessary If wiring and connections test properly but the fault persists, test each controller independently. Swap the ECM or HSC with a known-good unit to isolate the failed component. On high-hour used machines, controller capacitor degradation can cause intermittent communication failures even when bench-tested.

---

Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Komatsu service manual for your specific machine serial number and follow proper lockout/tagout procedures. For complex electrical diagnostics or controller replacement, professional consultation with a certified Komatsu technician is recommended.