Kobelco SK210-6E Fault Code D-2: Complete Diagnostic Guide

What is Kobelco SK210-6E Fault Code D-2?

Fault Code D-2 on the Kobelco SK210-6E indicates a malfunction in the engine preheating system, specifically related to the glow plug relay circuit or glow plug operation failure. This code is triggered when the Engine Control Module (ECM) detects abnormal resistance, voltage irregularities, or complete circuit failure in the preheating system that's essential for cold-start combustics in diesel engines.

The glow plug system on the SK210-6E is critical for proper engine starting, especially in cold weather conditions. When this system fails, the engine experiences difficulty achieving optimal combustion temperatures during startup, leading to hard starting, excessive white smoke, and potential long-term damage to injectors and cylinders. This code is particularly common in used excavators where electrical components have experienced years of vibration and temperature cycling.

Common Symptoms

• Hard starting or failure to start, especially in cold ambient temperatures below 40°F (4°C)
• Excessive white or gray smoke from the exhaust during initial startup that persists longer than normal
• Rough idle and misfiring for the first 2-3 minutes after cold start
• Warning light illumination on the instrument cluster indicating preheat system malfunction
• Extended cranking time required before engine fires, putting excessive strain on the starter motor

Potential Causes

The D-2 code on used SK210-6E excavators typically stems from several age-related issues:

• Faulty glow plug relay that fails to deliver proper voltage to the glow plug circuit (common failure point after 5,000+ hours)
• Burned out or damaged glow plugs due to carbon buildup or electrode deterioration
• Corroded or loose wiring connections at the glow plug harness, particularly at connector points near the engine block where moisture accumulates
• Damaged wiring harness with insulation breakdown from rubbing against the valve cover or fuel lines (known issue on SK210-6E models)
• Faulty ECM relay or internal ECM circuit board degradation affecting preheat circuit control
• Low battery voltage preventing adequate current flow to energize glow plugs properly

How to Troubleshoot and Fix Code D-2

Step 1: Perform Visual Inspection Begin by inspecting the glow plug wiring harness for visible damage, chafing, or corrosion. On used excavators, check connector pins for green corrosion buildup—especially at the junction near the cylinder head. Examine the glow plug relay (typically located in the fuse/relay box) for burn marks or corrosion on terminals.

Step 2: Test Glow Plug Relay and Circuit Voltage Using a digital multimeter (DMM), check for battery voltage (approximately 24V on SK210-6E systems) at the relay output terminal when the key is in the preheat position. If no voltage is present, test the relay by jumping terminals or replacing with a known-good relay. Measure voltage at each glow plug terminal—you should see consistent voltage across all plugs during the preheat cycle.

Step 3: Check Individual Glow Plug Resistance Disconnect the glow plug bus bar and measure resistance of each glow plug using your ohmmeter. Typical resistance should be 0.5-2.0 ohms for functional glow plugs. Any reading showing open circuit (infinite resistance) or significantly higher resistance indicates a failed glow plug requiring replacement.

Step 4: Inspect Wiring for Ground Faults Check for short circuits to ground by measuring resistance between the glow plug supply wire and chassis ground with all plugs disconnected. Any reading below 10,000 ohms indicates damaged insulation. Pay special attention to harness routing points where cables contact metal surfaces—a common wear point on used machines.

Step 5: Clear Code and Perform Functional Test After repairs, clear the fault code using Kobelco diagnostic software or by disconnecting the battery for 30 seconds. Perform a cold-start test to verify proper glow plug operation. Monitor preheat indicator lamp timing (should illuminate for 5-15 seconds depending on temperature) and confirm smooth engine start.

Critical Note for Used Excavators: Before replacing expensive components like the ECM or complete glow plug sets, thoroughly clean all electrical connections with electrical contact cleaner and apply dielectric grease. Many D-2 codes on high-hour machines resolve simply by addressing corroded connections—a fraction of the cost of component replacement.

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Disclaimer: This guide provides general troubleshooting information for the Kobelco SK210-6E fault code D-2. Always consult the manufacturer's service manual for model-specific specifications and torque values. If you're unfamiliar with electrical diagnostics or lack proper diagnostic tools, consult a certified Kobelco technician to prevent misdiagnosis and unnecessary component replacement.