Komatsu PC1250-11R Fault Code DA2RKR: Complete Diagnostic Guide

What is Komatsu PC1250-11R Fault Code DA2RKR?

Fault Code DA2RKR indicates a communication error between the machine's Engine Control Module (ECM) and the Hydraulic Control Module (HCM), specifically related to data transmission failure on the CAN bus network. This code is part of Komatsu's proprietary diagnostic system for the PC1250-11R model, which relies on continuous digital communication between control modules to optimize hydraulic performance and engine efficiency.

This fault is critical because the PC1250-11R uses integrated machine control where the ECM and HCM must exchange real-time data to manage engine load, hydraulic flow, and implement auto-deceleration features. When communication breaks down, the machine may enter a protective derate mode to prevent component damage, significantly reducing productivity on job sites.

Common Symptoms

When Code DA2RKR is active, operators typically experience:

• Amber or red warning lights on the monitor panel with communication error messages
• Reduced engine power or automatic engine speed limitation (derate mode activated)
• Sluggish hydraulic response or inconsistent boom/arm/bucket movements
• Intermittent loss of machine functions, particularly auto-idle or power mode switching
• Error messages displaying "CAN communication fault" or similar alerts on the LCD monitor

Potential Causes

The most common technical causes for DA2RKR on used PC1250-11R excavators include:

• Damaged or corroded CAN bus wiring harness between ECM and HCM (common wear point near engine firewall)
• Loose or oxidized connector pins at either the ECM or HCM connection points
• Failed termination resistors on the CAN network (typically 120-ohm resistors)
• ECM or HCM module failure due to voltage spikes, water intrusion, or age-related component degradation
• Faulty ground connections causing voltage reference issues between modules
• Aftermarket modifications or improper wiring repairs disrupting CAN bus integrity

How to Troubleshoot and Fix Code DA2RKR

Step 1: Visual Inspection Begin by inspecting the CAN bus harness routing between the ECM (located near the engine) and HCM (typically mounted near the hydraulic pumps). On used excavators, check for harness chafing against the engine block, heat damage near exhaust components, or rodent damage. Examine all connector pins for corrosion, bent terminals, or moisture intrusion.

Step 2: Electrical Testing Using a digital multimeter, verify CAN bus voltage. With ignition on, measure between CAN-High and CAN-Low terminals at both the ECM and HCM connectors—you should see approximately 2.5V differential (CAN-High ~3.5V, CAN-Low ~1.5V). Check termination resistance by measuring between CAN-High and CAN-Low with modules disconnected; you should read approximately 60 ohms (two 120-ohm resistors in parallel).

Step 3: Module and Software Verification Connect Komatsu KOMTRAX diagnostic software or compatible scan tool to read live data streams and verify both modules are communicating. Clear codes and monitor for recurrence. If wiring tests pass but communication fails, suspect ECM or HCM internal failure. For used machines, verify all software updates are current, as Komatsu has released patches addressing CAN communication stability.

Step 4: Harness and Connector Repair Replace any damaged wiring sections using proper gauge wire (typically 18-20 AWG twisted pair for CAN networks). Clean connector pins with electrical contact cleaner and apply dielectric grease to prevent future corrosion—critical for machines operating in harsh environments.

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Disclaimer: This guide provides general troubleshooting information. Always consult Komatsu service manuals specific to your machine's serial number and seek professional diagnostic assistance for complex electrical issues. Improper repairs to CAN bus systems can cause additional module damage.