Komatsu PC800SE-7 Fault Code DA2RMC: Complete Diagnostic Guide

What is Komatsu PC800SE-7 Fault Code DA2RMC?

Fault Code DA2RMC indicates a communication error between the Engine Control Module (ECM) and the Hydraulic Control Module (HCM) on the Komatsu PC800SE-7 excavator. This code specifically signals that the CAN bus communication network has detected an intermittent or complete loss of data transmission between these critical control systems.

The PC800SE-7 relies on continuous communication between the ECM and HCM to coordinate engine power output with hydraulic demand. When this communication fails, the machine cannot properly match engine speed to hydraulic load requirements, resulting in reduced operational efficiency and potential safety concerns. This is particularly critical in the PC800SE-7's advanced CLSS (Closed-Center Load Sensing System), which requires real-time data exchange for optimal performance.

Common Symptoms

When fault code DA2RMC is active, operators typically experience:

• Amber warning light illuminated on the monitor panel with reduced machine performance
• Engine derating or failure to respond properly to throttle inputs during heavy hydraulic loads
• Erratic hydraulic response with inconsistent swing, boom, or bucket speeds
• Intermittent loss of monitor display data showing engine parameters or hydraulic temperatures
• Machine entering limp mode with restricted travel speed and reduced hydraulic flow

Potential Causes

The most common technical causes for DA2RMC on used PC800SE-7 excavators include:

• CAN bus wiring harness damage at known rub points near the engine mounting brackets or along the right-hand chassis rail
• Corroded or loose connector pins at the ECM (located behind the operator cab) or HCM (mounted near the hydraulic pump)
• Failed termination resistor on the CAN bus network (120-ohm resistor failure)
• ECM or HCM internal communication circuit failure due to voltage spikes or age-related component degradation
• Contaminated or damaged connector seals allowing moisture intrusion in the engine compartment harness connections

How to Troubleshoot and Fix Code DA2RMC

Step 1: Visual Inspection Begin by inspecting all wiring harnesses between the ECM and HCM for visible damage, chafing, or pinch points. On used excavators, pay special attention to harness routing near the engine mounts where vibration causes wear. Check all connector seals for cracks or contamination.

Step 2: Connector and Resistance Testing Disconnect the CAN-H and CAN-L wires at both the ECM and HCM connectors. Using a digital multimeter, measure resistance between CAN-H and CAN-L terminals—you should read approximately 60 ohms (two 120-ohm termination resistors in parallel). Clean all connector pins with electrical contact cleaner and inspect for bent or corroded terminals.

Step 3: Advanced Diagnostics Connect Komatsu KOMTRAX diagnostic software or compatible scan tool to monitor live CAN bus communication. Check for voltage levels on CAN-H (approximately 3.5V) and CAN-L (approximately 1.5V) during operation. If voltage is absent or erratic, trace the harness for breaks or shorts to ground.

Step 4: Component Replacement If harness and connections test properly, suspect ECM or HCM failure. Before replacing expensive control modules on used equipment, verify battery voltage stability (12.5-14.5V) and check for loose ground connections at the chassis grounding points.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional assistance for complex electrical diagnostics.