Kobelco SK140LC-8 Fault Code B063: Complete Diagnostic Guide

What is Kobelco SK140LC-8 Fault Code B063?

Fault Code B063 indicates a malfunction in the engine preheater relay circuit. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects abnormal voltage or resistance in the glow plug preheater relay system, which is essential for cold-start operations in diesel engines.

The preheater relay controls power delivery to the glow plugs, which heat the combustion chambers before starting. On the Kobelco SK140LC-8, this system is critical for reliable cold-weather startups and smooth engine operation. When the ECM cannot properly activate or monitor this relay, it logs B063 and may affect starting performance, particularly in temperatures below 40°F (5°C).

Common Symptoms

Operators may experience the following when Code B063 is active:

• Hard starting or extended cranking time, especially in cold weather conditions
• Illuminated glow plug indicator light staying on longer than normal or flashing
• Engine warning lamp activation on the instrument cluster
• Rough idle or white smoke immediately after cold starts
• Error code stored in ECM memory even if starting eventually succeeds

Potential Causes

The most common technical causes for B063 on used SK140LC-8 excavators include:

• Failed preheater relay due to contact wear or coil burnout (common after 5,000+ operating hours)
• Corroded or loose electrical connectors at the relay socket or ECM harness junction
• Damaged wiring harness from engine vibration or rubbing against the engine block near the relay mounting location
• Blown fuse in the preheater circuit (typically 20-30A rating)
• ECM internal relay driver circuit failure (less common but possible in older units)
• Poor ground connection at engine block grounding points G101 or G102

How to Troubleshoot and Fix Code B063

Step 1: Visual Inspection Locate the preheater relay (usually mounted on the engine firewall or relay panel). Inspect all connectors for corrosion, bent pins, or heat damage. Check the wiring harness for chafing points where it contacts the engine—this is a known wear area on used machines.

Step 2: Test the Relay Remove the preheater relay and test it with a multimeter. Apply 12V to the coil terminals and check for continuity across the switch terminals. Resistance should drop to near 0 ohms when energized. Replace if the relay fails to click or shows infinite resistance.

Step 3: Check Circuit Voltage Using Kobelco diagnostic software (KANSS) or a multimeter, verify battery voltage (12-14V) at the relay power supply terminal with the key in the "preheat" position. Check the ECM signal wire for switching voltage (0V to 12V transition).

Step 4: Inspect Fuses and Grounds Verify the preheater circuit fuse integrity and check ground continuity between the relay mounting point and battery negative. Resistance should be less than 0.5 ohms. Clean and tighten all ground connections.

Step 5: Clear Code and Test After repairs, clear the fault code using diagnostic software and perform a cold-start test to verify proper preheater operation.

---

Disclaimer: This guide provides general troubleshooting information. For safety and warranty protection, consult a certified Kobelco technician or authorized service center, especially when working with electrical systems on used heavy equipment.