What is Komatsu PC240LC-10 Fault Code DA2QKR?

Fault Code DA2QKR on the Komatsu PC240LC-10 excavator indicates a communication error between the Engine Control Module (ECM) and the Machine Control Module (MCM), specifically related to CAN bus data transmission failure. This code triggers when the controller area network experiences an interruption or corruption in signal exchange between these critical control units.

This fault is particularly significant for the PC240LC-10 because the ECM and MCM must continuously share operational data to coordinate engine performance with hydraulic functions, implement fuel efficiency protocols, and manage emissions systems. When communication breaks down, the machine cannot properly synchronize powertrain demands with hydraulic load requirements, potentially causing erratic behavior or entering a protective derate mode. For used excavators, this code often surfaces due to age-related wiring degradation or connector corrosion rather than module failure.

Common Symptoms

• Machine Controller Warning Light illuminated on the monitor panel with reduced engine power output
• Intermittent or complete loss of hydraulic response during combined functions (swing with boom operation)
• Engine failing to respond properly to throttle inputs or stuck in low-idle mode
• Diagnostic monitor displaying multiple simultaneous fault codes alongside DA2QKR
• Unexpected shutdown or failure to start, particularly in cold weather conditions

Potential Causes

The most common technical causes for DA2QKR on used PC240LC-10 excavators include:

• CAN bus wiring harness damage from rubbing against the boom cylinder or frame rails near the engine compartment
• Corroded or moisture-infiltrated Deutsch connectors at the ECM or MCM junction points (common failure point after 5,000+ hours)
• Failed termination resistors on the CAN network causing signal reflection and data corruption
• ECM or MCM internal faults, though less common than harness issues in used machines
• Low battery voltage (below 22V on 24V systems) causing communication dropout during cranking
• Aftermarket component installations that created grounding issues or electromagnetic interference

How to Troubleshoot and Fix Code DA2QKR

Step 1: Visual Harness Inspection Begin by physically tracing the main wiring harness from the ECM (located behind the operator cab) to the MCM (typically mounted near the hydraulic pump). On used excavators, inspect for chafing where the harness passes through the rotating deck interface and near the boom base. Look for abraded insulation, exposed copper, or oil-soaked wiring that indicates seal leaks contaminating connections.

Step 2: Connector and Voltage Testing Disconnect the 20-pin CAN bus connector at both the ECM and MCM. Using a multimeter, check for corrosion on pins 6 and 14 (CAN-H and CAN-L respectively). Measure resistance between CAN-H and CAN-L with the key off—you should read approximately 60 ohms if termination resistors are functional. Test battery voltage at the ECM power supply; it must exceed 24V during cranking to maintain stable communication.

Step 3: Advanced Diagnostics with Komatsu Software Connect Komatsu Diagnostic Explorer (KTEC) or equivalent diagnostic software to the machine's diagnostic port. Monitor live CAN bus traffic while cycling the ignition. Look for message timeout errors or corrupted data frames. If communication is intermittent, perform a wiggle test on all connectors while monitoring—movement that disrupts communication pinpoints the faulty connection. For used machines, replacing the entire engine-to-frame harness section (Komatsu part 20Y-06-31614) often resolves persistent issues more cost-effectively than chasing individual wire repairs.

Step 4: Module and Termination Resistor Verification If wiring and connectors pass inspection, test the 120-ohm termination resistors located at each end of the CAN network. Use your multimeter to confirm each resistor reads 120 ohms ±5%. Replace any resistor outside this range. Only after confirming wiring integrity should you consider ECM or MCM replacement—these modules rarely fail unless exposed to voltage spikes or water intrusion.

---

Disclaimer: This guide provides general troubleshooting information for the Komatsu PC240LC-10. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic support for complex electrical issues. Improper repairs can cause additional system damage or safety hazards.