What is Kobelco SK200-6E Fault Code B-2?

Kobelco SK200-6E Fault Code B-2 indicates a malfunction in the engine preheating system, specifically related to the glow plug relay circuit or glow plug operation. This code is triggered when the Engine Control Module (ECM) detects abnormal current flow, resistance, or voltage in the glow plug circuit during the pre-start heating cycle.

The glow plug system is critical for cold-start performance on the Isuzu 6BG1 diesel engine found in the SK200-6E. When this circuit fails, the engine may experience hard starting, excessive white smoke during startup, and increased wear on internal components due to incomplete combustion during the warm-up phase. For used excavators operating in cold climates, a functioning preheating system is essential to prevent premature engine damage and ensure reliable daily operation.

Common Symptoms

• Hard starting or extended cranking time, especially in cold weather conditions (below 40°F/4°C)
• Glow plug indicator light fails to illuminate on the instrument panel, or stays illuminated longer than normal
• Excessive white or gray smoke from the exhaust during initial startup that persists longer than usual
• Rough idle and misfiring for the first several minutes after cold start
• Check engine light remains active on the dashboard after engine reaches operating temperature

Potential Causes

The B-2 fault code on used SK200-6E excavators typically stems from age-related electrical deterioration. The most common causes include:

• Failed glow plug relay located near the engine ECM mounting bracket (known failure point on 6BG1 engines with 8,000+ operating hours)
• Burned-out individual glow plugs creating unbalanced current draw that triggers circuit protection
• Corroded or loose connections at the glow plug harness connector, particularly where the harness passes over the valve cover
• Damaged wiring harness due to heat exposure or rubbing against the engine block near cylinder head mounting points
• ECM internal relay failure (less common but possible on machines manufactured before 2002)
• Low battery voltage preventing adequate current supply to the glow plug circuit during activation

How to Troubleshoot and Fix Code B-2

Step 1: Visual Inspection and Preliminary Checks Begin by inspecting the glow plug harness for visible damage, particularly where it routes across the valve cover and near the turbocharger heat shield. Check all connector pins for corrosion or burn marks. On used excavators, this harness commonly suffers from heat degradation. Use a multimeter to verify battery voltage exceeds 12.4V with the engine off.

Step 2: Test Glow Plug Relay and Circuit Locate the glow plug relay (typically a black rectangular unit mounted near the ECM). With the key in the ON position (engine not running), listen for an audible click when the relay energizes. Using a multimeter set to DC voltage, backprobe the relay output terminal—you should read full battery voltage (12V+) for approximately 15-30 seconds during the preheat cycle.

Step 3: Individual Glow Plug Resistance Testing Disconnect the glow plug bus bar and test each glow plug individually using a multimeter set to ohms. Each plug should read between 0.5-2.0 ohms resistance. Replace any glow plugs reading open circuit (infinite resistance) or significantly lower than 0.5 ohms. For used machines, replacing all glow plugs as a set prevents repeat failures.

Step 4: Harness Continuity and Ground Testing Check continuity from the relay output to each glow plug terminal. Inspect the ground connection at the cylinder head—corrosion here causes high resistance that triggers the B-2 code. Clean ground points with a wire brush and apply dielectric grease before reconnection.

Step 5: Clear Code and Verify Repair After repairs, clear the fault code using Kobelco diagnostic software or by disconnecting the battery negative terminal for 30 seconds. Perform a cold-start test to verify the glow plug system operates correctly and the code does not return.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Kobelco service manual for your specific serial number and follow proper safety procedures. If you're unfamiliar with electrical diagnostics or working on diesel fuel systems, seek assistance from a certified heavy equipment mechanic.