Komatsu PC70-8 Fault Code DA2RMC: Complete Diagnostic Guide

What is Komatsu PC70-8 Fault Code DA2RMC?

Fault Code DA2RMC indicates a communication error between the machine's main controller (ECM) and the hydraulic pump control system, specifically related to the pump regulator solenoid circuit.

This code is part of Komatsu's proprietary diagnostic system and signals that the Electronic Control Module (ECM) cannot properly communicate with or control the hydraulic pump's electronic regulator. The PC70-8 relies on precise hydraulic flow management for optimal performance, making this communication pathway critical. When this circuit fails, the machine cannot properly modulate hydraulic pressure based on load demands, directly impacting operational efficiency and potentially causing component damage if left unaddressed.

Common Symptoms

When DA2RMC is active on your PC70-8, operators typically experience:

• Reduced hydraulic power across all functions (boom, arm, bucket, swing)
• Intermittent or complete loss of fine control during precision work
• Warning lamp illumination on the instrument cluster (typically amber/yellow)
• Engine derate mode where RPM is limited to protect the system
• Erratic hydraulic response with delayed or jerky movements during operation

Potential Causes

The most common technical causes for DA2RMC on used PC70-8 excavators include:

• Damaged wiring harness between the ECM and pump regulator solenoid, particularly at flex points near the pump mounting area
• Corroded or loose connector pins at the pump solenoid connector (common in machines exposed to moisture)
• Failed pump regulator solenoid due to internal coil breakdown or mechanical seizure
• ECM internal fault affecting the output driver circuit for pump control
• Voltage supply issues from damaged power distribution harness or poor ground connections
• Contaminated hydraulic oil causing solenoid valve sticking (secondary electrical symptom)

How to Troubleshoot and Fix Code DA2RMC

Step 1: Visual Inspection Begin by inspecting the wiring harness running from the main ECM (located under the operator's cab) to the hydraulic pump regulator solenoid. On used excavators, check for harness chafing against the pump housing, heat damage from nearby components, or rodent damage. Inspect all connector pins for corrosion, bent terminals, or oil contamination.

Step 2: Electrical Testing Using a digital multimeter, check the pump regulator solenoid resistance. Typical specifications are 8-15 ohms (consult your service manual). Disconnect the solenoid connector and measure resistance across the solenoid terminals. Next, check for supply voltage at the connector with the ignition on—you should see battery voltage (12-14V). Verify ground continuity by measuring resistance between the solenoid ground pin and chassis ground (should be less than 1 ohm).

Step 3: Advanced Diagnostics Connect Komatsu KOMTRAX diagnostic software or a compatible scan tool to read live data and perform actuator tests. Command the pump solenoid on/off while monitoring current draw. Normal operation shows 0.8-1.2 amps. If electrical tests pass but the code persists, inspect the ECM connector for corrosion and consider ECM replacement as a last resort.

Step 4: Used Equipment Considerations For older PC70-8 machines, always check for previous repair attempts that may have introduced wiring modifications. Inspect harness routing for improper securing that causes vibration damage. Replace any weatherpack connectors showing signs of moisture intrusion, as this is a common failure point on machines with 3,000+ operating hours.

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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 or ECM replacement procedures.