What is Kobelco SK210-6E Fault Code G-3?

Fault Code G-3 on the Kobelco SK210-6E indicates a malfunction in the engine revolution sensor circuit, specifically detecting an abnormal signal or loss of communication between the engine speed sensor and the Engine Control Module (ECM). This code is part of Kobelco's proprietary diagnostic system designed to monitor critical engine parameters on their sixth-generation excavators.

The engine revolution sensor (also called the crankshaft position sensor) provides real-time RPM data to the ECM, which uses this information to control fuel injection timing, pump output, and overall engine performance. When Code G-3 triggers, the ECM cannot accurately determine engine speed, compromising the machine's ability to operate efficiently. On the SK210-6E, this fault can cause the excavator to enter a protective derate mode or prevent starting altogether, making it a critical issue for operational uptime.

Common Symptoms

When Code G-3 is active on your Kobelco SK210-6E, you may experience:

• Engine fails to start or cranks but won't fire due to lack of RPM signal confirmation
• Warning light illuminated on the instrument cluster with fault code displayed on monitor panel
• Sudden engine shutdown during operation, particularly under load conditions
• Erratic engine behavior including unstable idle, surging RPM, or unexpected power loss
• Black smoke emission from exhaust due to incorrect fuel injection timing

Potential Causes

The most common technical causes for Code G-3 on used SK210-6E excavators include:

• Failed engine revolution sensor due to internal component degradation or heat damage (common failure point on machines with 6,000+ hours)
• Damaged wiring harness between sensor and ECM, particularly where harness runs along engine block and experiences vibration wear
• Corroded or loose connector pins at the sensor plug or ECM connector (highly prevalent in machines exposed to moisture or stored outdoors)
• ECM internal fault preventing proper signal interpretation (less common but possible on high-hour units)
• Broken sensor mounting allowing excessive air gap between sensor and reluctor ring on flywheel
• Magnetic debris accumulation on sensor tip interfering with signal generation

How to Troubleshoot and Fix Code G-3

Step 1: Visual Inspection Begin by locating the engine revolution sensor, typically mounted on the flywheel housing near the starter motor. Inspect the sensor body for physical damage, cracks, or oil contamination. Check the wiring harness from sensor to ECM for visible damage, particularly where it routes near heat sources or moving components. On used excavators, examine connector pins closely for corrosion (green/white deposits) or bent terminals.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. The Kobelco specification typically calls for 800-1200 ohms at room temperature (consult your service manual for exact values). Next, check for continuity in the wiring harness from sensor connector to ECM pins. Measure voltage supply from the ECM to the sensor—you should see approximately 8-12 volts with ignition on. Any deviation indicates wiring issues or ECM problems.

Step 3: Air Gap Verification If electrical values check out, verify the air gap between the sensor tip and flywheel reluctor ring. The proper gap should be 0.5-1.5mm. Use a feeler gauge to confirm clearance. On used machines with wear, the mounting bracket may have loosened or shifted.

Step 4: Component Replacement Replace the engine revolution sensor with a genuine Kobelco or OEM-equivalent part. After installation, clear the fault code using Kobelco diagnostic software (SICS service software) or by disconnecting the battery negative terminal for 10 minutes. Start the engine and verify code does not return.

Used Equipment Note: Before replacing expensive components, thoroughly inspect harness routing and connector integrity—these account for 60-70% of sensor-related codes on older SK210-6E models.

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Disclaimer: This guide provides general troubleshooting information. Always consult a certified Kobelco technician and refer to the official service manual for your specific machine serial number before performing repairs. Improper diagnosis may lead to additional component damage.