What is Kobelco SK350LC-8 Fault Code B024?

Fault Code B024 on the Kobelco SK350LC-8 excavator indicates a malfunction in the engine preheating system, specifically an abnormal voltage or open circuit detected in the glow plug relay circuit. This code is generated when the Engine Control Module (ECM) detects that the glow plug system is not functioning within specified parameters, preventing proper cold-start operation.

The glow plug preheating system is critical for diesel engine starting, especially in cold ambient temperatures. On the SK350LC-8, this system uses a relay-controlled circuit to energize the glow plugs, heating the combustion chambers before and during cranking. When the ECM cannot confirm proper relay operation or detects voltage irregularities in the control circuit, it sets B024 and may limit engine starting capability. For used excavators operating in cold climates or experiencing extended idle periods, a functioning preheating system is essential to prevent hard starting and reduce wear on starter components.

Common Symptoms

• Glow plug indicator light remains illuminated continuously or fails to activate during the normal preheating cycle
• Difficult cold starts requiring extended cranking, particularly in temperatures below 50°F (10°C)
• Excessive white smoke during initial startup due to incomplete combustion from cold cylinders
• Engine cranks but fails to start in cold conditions, though may start normally when warm
• B024 fault code displayed on the multi-information display or retrieved via diagnostic software

Potential Causes

The most common technical causes of B024 on used SK350LC-8 excavators include:

• Glow plug relay failure due to contact wear, coil resistance degradation, or internal short circuits (common in machines with 5,000+ operating hours)
• Corroded or loose electrical connections at the relay socket, harness connector near the battery box, or ground points—frequently caused by battery acid exposure
• Damaged wiring harness with chafing or insulation breakdown along the routing path from the ECM through the engine compartment firewall
• Faulty ECM power supply to the glow plug control circuit, including blown fuses or poor connections at the main relay panel
• Failed individual glow plugs creating abnormal current draw that triggers relay circuit protection
• Voltage drop issues in the main battery supply system affecting relay coil energization (common in machines with aging battery cables)

How to Troubleshoot and Fix Code B024

Step 1: Initial System Verification Connect Kobelco-compatible diagnostic software (such as KENR or equivalent aftermarket scan tool) to retrieve freeze frame data and confirm B024 is current. Check the battery voltage—ensure it maintains 12.5-13V minimum with the key off and 13.8-14.4V when running. Low voltage can cause false relay circuit faults. Inspect all battery cable connections and clean any corrosion at terminals.

Step 2: Glow Plug Relay Inspection Locate the glow plug relay in the main relay panel (typically under the operator cab near the battery compartment). Remove the relay and inspect the socket for corrosion, melted terminals, or moisture intrusion—common issues in used excavators. Using a digital multimeter, test relay coil resistance between terminals 85 and 86; specification is typically 70-90 ohms. Test contact resistance between terminals 30 and 87 when the relay is manually activated—should read less than 0.5 ohms. Replace the relay if readings are out of specification.

Step 3: Circuit Voltage and Continuity Testing With the relay removed and ignition key in the ON position (engine not running), measure voltage at relay socket terminal 85 (control circuit from ECM)—should read battery voltage during the glow plug preheating cycle (typically 10-30 seconds after key-on). If no voltage is present, check for open circuits or damaged wiring between the ECM connector (pin specific to your model year) and the relay socket. Inspect harness routing for chafing points near frame brackets and through bulkhead grommets.

Step 4: Load-Side Circuit Testing Measure voltage at relay socket terminal 30 (power supply)—should read constant battery voltage. Check the fuse or fusible link protecting this circuit. Test continuity from relay terminal 87 to the glow plug bus bar—should show less than 1 ohm resistance. For used excavators, physically inspect this heavy-gauge wire for corrosion at crimp connections and verify the bus bar mounting bolts are tight.

Step 5: Glow Plug Verification If relay and wiring circuits test correctly, measure individual glow plug resistance. Disconnect the bus bar and test each glow plug using a multimeter—specification is typically 0.5-2.0 ohms depending on type. A failed glow plug (open circuit or drastically different resistance) can cause abnormal current draw affecting the relay circuit. On high-hour used machines, replacing all glow plugs as a set is recommended if one has failed.

Step 6: Clear Code and Verify Repair After repairs, clear the fault code using diagnostic software and perform a key-on glow plug cycle while monitoring live data. Verify the ECM commands relay activation and proper voltage/current flow occurs. Test-start the engine in cold conditions if possible to confirm normal operation.

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Disclaimer: This guide provides general troubleshooting procedures for informational purposes. Always consult the official Kobelco service manual for your specific machine serial number and model year. If you're unfamiliar with electrical diagnostics or high-current circuits, seek assistance from a certified heavy equipment technician to prevent injury or equipment damage.