What is Kobelco SK130-8 Fault Code B104?

Kobelco SK130-8 Fault Code B104 indicates a malfunction in the engine preheating system, specifically related to the glow plug relay circuit or glow plug indicator lamp circuit. This diagnostic trouble code (DTC) is stored in the Engine Control Module (ECM) when abnormal voltage or resistance is detected in the preheating circuit that helps diesel combustion during cold starts.

This code is critical for the SK130-8's performance because the glow plug system ensures proper fuel atomization and ignition in cold operating conditions. When B104 is active, the engine may experience difficult cold starts, increased white smoke during startup, and rough idling until operating temperature is reached. For used excavators operating in colder climates, this fault can significantly impact daily productivity and increase engine wear.

Common Symptoms

• Glow plug indicator light remains illuminated on the instrument panel or fails to light during the preheating cycle
• Hard starting or extended cranking time, especially in temperatures below 50°F (10°C)
• Excessive white or gray smoke during cold engine startup that persists longer than normal
• Rough engine idle for the first several minutes of operation until the engine reaches normal operating temperature
• Check Engine light illuminated on the dashboard with stored fault code B104

Potential Causes

The most common causes of B104 on used SK130-8 excavators include:

• Faulty glow plug relay that fails to complete the circuit or has corroded internal contacts (common failure point after 5,000+ hours)
• Damaged wiring harness between the ECM and glow plug relay, particularly where the harness passes near the engine block and experiences heat cycling and vibration
• Poor electrical connections at the glow plug relay connector or ECM connector due to moisture intrusion or corrosion
• Failed individual glow plugs causing irregular current draw that triggers the circuit fault
• ECM internal fault in the glow plug control circuit (less common but possible in high-hour machines)
• Blown fuse in the glow plug power supply circuit

How to Troubleshoot and Fix Code B104

Step 1: Visual Inspection and Code Verification Connect a Kobelco diagnostic tool or compatible scan tool to retrieve and confirm fault code B104. Inspect the glow plug relay (typically located in the engine compartment fuse/relay box) and all associated wiring harnesses for obvious damage, corrosion, or signs of overheating. On used excavators, pay special attention to harness sections that may have rubbed against the engine block or frame.

Step 2: Test Glow Plug Relay and Circuit Using a digital multimeter, test the glow plug relay by checking for battery voltage (12V) at the relay power supply terminal with the key in the ON position. Test relay operation by listening for an audible click during the preheating cycle. Remove the relay and bench-test it by applying 12V DC to the control terminals and verifying continuity through the load circuit. Check relay connector pins for corrosion or bent terminals.

Step 3: Check Glow Plug Resistance and Harness Continuity Disconnect the glow plug harness and measure individual glow plug resistance. Typical specification is 0.5-2.0 ohms per glow plug (consult Kobelco service manual for exact values). Test harness continuity from the relay to each glow plug connection and from the relay control wire back to the ECM connector. On used machines with high operating hours, corroded connectors at the glow plugs are common and should be cleaned with electrical contact cleaner before reassembly.

Step 4: Verify ECM Signal and Clear Code Check the ECM connector for moisture, corrosion, or pushed-back pins. Verify the ECM is sending the proper ground signal to activate the relay during preheating. After repairs, clear the fault code and perform a cold start test to confirm proper glow plug operation and code resolution.

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Disclaimer: This guide provides general troubleshooting information for Kobelco SK130-8 fault code B104. Always consult the manufacturer's service manual for precise specifications and procedures. If you're uncomfortable performing electrical diagnostics, contact a certified Kobelco technician or qualified heavy equipment mechanic for professional assistance.