Komatsu PC240LC-8 Fault Code DA2RMC: Technical Guide

What is Komatsu PC240LC-8 Fault Code DA2RMC?

Fault Code DA2RMC indicates a "Revolution Sensor 2 Abnormal Signal" error in the Komatsu PC240LC-8 excavator's engine control system. This code is triggered when the Electronic Control Module (ECM) detects an irregular or missing signal from the secondary engine speed sensor, also known as Revolution Sensor 2 or the camshaft position sensor.

This sensor is critical for the PC240LC-8's SAA6D107E-1 engine because it provides essential timing data to the ECM for proper fuel injection control, ignition timing, and overall engine synchronization. When this sensor fails or sends erratic signals, the ECM cannot accurately determine engine position, which directly impacts combustion efficiency, power output, and emissions control. In used excavators, this code often appears due to sensor degradation, wiring harness damage, or connector corrosion from years of exposure to hydraulic oil mist and vibration.

Common Symptoms

When fault code DA2RMC is active on your Komatsu PC240LC-8, operators typically experience:

• Check Engine Warning Light or malfunction indicator illuminated on the monitor panel
• Engine derate mode activated, limiting maximum RPM to protect the engine (typically reduced to 1,500-1,800 RPM)
• Rough idling or inconsistent engine performance, particularly during cold starts
• Difficult starting conditions, requiring extended cranking time before the engine fires
• Reduced hydraulic power and sluggish response due to restricted engine speed

Potential Causes

The most common technical causes for DA2RMC on used PC240LC-8 excavators include:

• Revolution Sensor 2 failure due to internal component degradation or heat damage from prolonged operation
• Wiring harness damage at known rub points near the engine block or fuel injection pump mounting area
• Corroded or loose connector pins on the sensor plug, especially on machines with 5,000+ operating hours
• ECM internal fault or corrupted sensor calibration data (less common but possible in high-hour machines)
• Damaged sensor reluctor ring or flywheel teeth causing intermittent signal dropout
• Electromagnetic interference from aftermarket electrical accessories or poor grounding

How to Troubleshoot and Fix Code DA2RMC

Step 1: Initial Diagnostic Scan Connect a Komatsu diagnostic software tool (KOMTRAX Plus or compatible scan tool) to retrieve freeze frame data and verify the fault is current, not historic. Check if multiple codes are present, which may indicate a broader ECM or power supply issue.

Step 2: Visual Inspection Physically inspect Revolution Sensor 2, located on the engine timing case near the camshaft gear. Look for physical damage, oil contamination, or gap issues (proper air gap should be 0.5-1.5mm). On used excavators, pay special attention to the wiring harness routing from the sensor to the ECM, checking for abraded insulation at common rub points against the engine block and hydraulic lines.

Step 3: Electrical Testing Disconnect the sensor connector and measure resistance across the sensor terminals using a multimeter (typical specification: 190-250 ohms at 20°C). Test the wiring harness for continuity from sensor connector to ECM pins, and check for shorts to ground. Measure supply voltage from the ECM (should be approximately 8-12V DC).

Step 4: Sensor Replacement and Verification If testing confirms sensor failure, replace Revolution Sensor 2 with a genuine Komatsu part (part number 6754-21-9130 or equivalent). After installation, clear the fault code and perform a test run under load, monitoring for code recurrence. For used machines, apply dielectric grease to connector pins to prevent future corrosion.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Komatsu PC240LC-8 service manual and consider professional diagnostic services for complex electrical issues. Improper repairs may cause further damage or safety hazards.