What is Komatsu Fault Code E606?

Komatsu fault code E606 indicates a malfunction in the engine control system's communication circuit, specifically a CAN (Controller Area Network) communication error between the engine ECM (Engine Control Module) and other control units. This code typically appears when the electronic control modules cannot properly exchange data over the machine's communication network, disrupting critical system coordination.

The CAN bus system serves as the central nervous system for modern Komatsu excavators, enabling real-time data exchange between the engine controller, hydraulic systems, instrument cluster, and other electronic components. When communication fails, the ECM cannot receive vital operating parameters or send control commands effectively. This fault is particularly critical because it can trigger limp mode or emergency derate, significantly limiting machine productivity and potentially masking other underlying issues that require attention.

Common Symptoms

• Warning lights illuminating on the instrument panel, including the check engine light and potentially the hydraulic system warning indicator
• Reduced engine power or activation of derate mode, limiting RPM and hydraulic performance to protect the machine
• Intermittent or complete loss of instrument cluster functions, including inaccurate gauge readings or blank display screens
• Erratic hydraulic performance with delayed or unresponsive control inputs due to communication delays
• Multiple fault codes appearing simultaneously as different systems lose communication capability

Potential Causes

The most common technical failures triggering E606 in used Komatsu excavators include:

• Damaged or corroded CAN bus wiring harness, particularly at known rub points near the engine mount, swing bearing, or along the boom where vibration and movement cause wear
• Loose or corroded connector pins at the ECM, instrument cluster, or junction boxes exposed to moisture infiltration
• Failed termination resistors on the CAN network endpoints, which are essential for proper signal integrity
• ECM power supply issues including low voltage, poor grounds, or failing main relays affecting controller operation
• Physical damage to control modules from vibration, heat exposure, or water intrusion common in older machines

How to Troubleshoot and Fix Code E606

Step 1: Visual Inspection Begin with a thorough physical examination of all wiring harnesses along the main chassis, particularly checking areas where cables pass through bulkheads or near moving components. Look for abraded insulation, pinched wires, or evidence of rodent damage. Inspect all connector housings for corrosion, bent pins, or moisture presence—this is especially critical in used excavators with compromised seals.

Step 2: Electrical Testing Using a digital multimeter, verify proper voltage supply to the ECM (typically 24V on Komatsu machines) and check for clean ground connections with less than 0.5 ohms resistance. Test CAN bus continuity between communication pins (typically CAN-High and CAN-Low) at multiple connector points. Measure termination resistance across the network; you should read approximately 60 ohms with the key off, indicating proper termination resistors.

Step 3: Advanced Diagnostics Connect Komatsu diagnostic software (KOMTRAX or authorized scan tool) to read live data and monitor communication status between modules. Check for intermittent dropouts during engine operation. If harnesses and connections test properly, suspect ECM internal failure or corrupted software requiring module reprogramming or replacement.

Critical for Used Equipment: Before replacing expensive control modules, thoroughly inspect all connector terminals for "green corrosion" and apply dielectric grease after cleaning. Check for previous repair attempts including aftermarket harness splices that may have degraded over time.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific model and consider engaging a certified technician for complex electrical diagnostics and repairs.