What is Kobelco SK140LC-8 Fault Code 20008?

Fault Code 20008 on the Kobelco SK140LC-8 excavator indicates a malfunction in the engine control system, specifically related to the Engine Control Module (ECM) communication error or main relay circuit abnormality. This code triggers when the ECM detects a loss of proper voltage supply, a short circuit in the main relay circuit, or interrupted communication between the control unit and the engine's electrical system.

This fault is critical for the SK140LC-8 because the main relay controls power distribution to essential engine management components. When this circuit fails, the ECM cannot properly regulate fuel injection timing, monitor sensor inputs, or manage emissions controls. For used excavators, this code often appears due to age-related electrical degradation, making it a common concern for buyers evaluating pre-owned Kobelco machines.

Common Symptoms

When Code 20008 is active on your SK140LC-8, you may experience:

• Engine cranks but fails to start, or starts then immediately shuts down
• Warning light illumination on the instrument cluster, often accompanied by a check engine indicator
• Intermittent power loss or unexpected engine shutdowns during operation
• Complete loss of electronic throttle control, preventing normal RPM adjustment
• Diagnostic display showing error code 20008 when scanned with Kobelco diagnostic software

Potential Causes

Several factors commonly trigger this fault code in used SK140LC-8 excavators:

• Main relay failure due to internal contact wear or coil degradation (common after 5,000+ operating hours)
• Corroded or loose connections at the ECM harness connector, particularly at the C101 main power connector
• Damaged wiring harness between the main relay and ECM, often caused by rubbing against the engine block near the fuel filter mounting area
• Blown fuses in the engine compartment fuse box, specifically the ECM power supply fuse
• Faulty ECM ground connections (G102 ground point), especially in machines exposed to wet conditions
• Voltage drops in the battery or charging system causing insufficient power delivery to the ECM

How to Troubleshoot and Fix Code 20008

Step 1: Perform Initial Visual Inspection Begin by checking the engine compartment fuse box for blown fuses related to the ECM circuit. Inspect the main relay (typically located in the electrical box near the battery) for signs of heat damage, corrosion, or loose mounting. For used excavators, pay special attention to connector terminals for green corrosion or pushed-back pins.

Step 2: Test Main Relay Operation Using a multimeter, measure voltage at the relay coil terminals with the key switch in the ON position—you should see battery voltage (approximately 24V for this model). Next, check for continuity across the relay contact terminals when energized. If the relay doesn't click audibly or shows infinite resistance when activated, replace the main relay (Kobelco part number typically YN20M00036P1 or equivalent).

Step 3: Inspect ECM Harness and Connections Disconnect the ECM main connector (C101) and carefully inspect for corrosion, moisture, or damaged pins. On used machines, check the harness routing between the relay box and ECM for worn insulation—the SK140LC-8 has a known rub point near the air filter housing. Clean all connections with electrical contact cleaner and apply dielectric grease before reconnecting.

Step 4: Verify Ground Connections and Voltage Supply Locate ground point G102 (usually on the engine block near the starter) and remove, clean, and retighten the connection. With the key ON and engine OFF, measure voltage at the ECM power supply pin—it should show stable battery voltage. Any reading below 23V indicates charging system problems that must be addressed first.

Step 5: Advanced Diagnostics If the above steps don't resolve the issue, connect Kobelco diagnostic software (CAPS II or equivalent) to monitor real-time ECM power supply voltage and relay command signals. This will confirm whether the ECM itself is faulty or if intermittent wiring issues exist.

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Disclaimer: This guide provides general diagnostic information for Kobelco SK140LC-8 excavators. Electrical system repairs should be performed by qualified diesel technicians with proper training. Always consult the official Kobelco service manual and follow lockout/tagout procedures before performing electrical diagnostics. Improper repairs may cause further damage or safety hazards.