What is Kobelco SK140 Fault Code 06568?

Fault Code 06568 on the Kobelco SK140 excavator indicates an abnormality in the fuel injection system's common rail pressure control circuit, specifically related to a deviation between commanded and actual rail pressure values. This diagnostic trouble code (DTC) is generated by the Engine Control Module (ECM) when it detects that the fuel rail pressure cannot maintain the target pressure within acceptable parameters during engine operation.

This code is particularly critical for the SK140 because the common rail fuel injection system relies on precise pressure control (typically 1,200-1,800 bar) to optimize combustion efficiency, power output, and emissions compliance. When this system fails, the excavator cannot deliver proper fuel atomization, directly impacting performance and potentially causing long-term engine damage. For used excavators, this code often signals wear-related issues in high-pressure fuel components that have accumulated thousands of operating hours.

Common Symptoms

When Code 06568 is active, operators typically experience:

• Engine power derate or noticeable loss of hydraulic performance during digging and lifting operations
• Rough idling or intermittent stalling, especially during cold starts or low-load conditions
• Black or white exhaust smoke indicating improper fuel combustion due to pressure inconsistencies
• Check engine light (CEL) illuminated on the instrument panel with possible amber warning indicators
• Difficulty starting or extended cranking time before the engine fires, particularly after the machine has been sitting

Potential Causes

The most common technical causes for Code 06568 on used SK140 excavators include:

• Fuel pressure regulator valve failure – the solenoid controlling rail pressure becomes stuck or responds sluggishly due to carbon buildup or internal wear
• Rail pressure sensor malfunction – contaminated fuel or age-related drift causes inaccurate pressure readings sent to the ECM
• High-pressure fuel pump wear – internal components (plungers, seals) lose efficiency after extended use, reducing maximum achievable pressure
• Injector internal leakage – one or more injectors with worn nozzles cause pressure drop across the common rail system
• Wiring harness damage at sensor connections, particularly where harnesses run near the engine block and experience heat cycling and vibration
• Fuel supply issues including clogged fuel filters, contaminated diesel, or air ingestion in used machines with aging fuel systems

How to Troubleshoot and Fix Code 06568

Step 1: Connect Diagnostic Software Use Kobelco-specific diagnostic software or a compatible scan tool to read live data parameters. Monitor actual vs. commanded rail pressure values during idle and under load. A deviation exceeding 100-150 bar typically confirms the fault. Document fuel pressure readings at various engine RPMs.

Step 2: Inspect Rail Pressure Sensor and Wiring Physically inspect the fuel rail pressure sensor mounted on the common rail assembly. Check connector pins for corrosion, bent terminals, or fuel contamination – common issues in used excavators. Using a digital multimeter, verify sensor supply voltage (typically 5V reference) and ground continuity. Inspect the wiring harness for chafing points where it contacts the engine block or routing brackets, as vibration damage frequently occurs here in higher-hour machines.

Step 3: Test Fuel Pressure Regulator Operation Locate the pressure control valve (PCV) on the high-pressure pump assembly. Using diagnostic software, command the valve through its operational range while monitoring pressure response. Measure resistance across the solenoid terminals (typically 2-6 ohms). Remove and physically inspect the valve for carbon deposits or mechanical binding – replace if response is sluggish or resistance is out of specification.

Step 4: Evaluate High-Pressure Fuel System Components Perform a fuel return quantity test on each injector to identify internal leakage. Excessive return flow from any injector indicates worn nozzles contributing to pressure loss. Check the high-pressure fuel pump output capacity using manufacturer specifications. On used excavators, examine all high-pressure fuel lines for external seepage or micro-cracks at ferrule connections, which cause pressure instability. Replace fuel filters and verify fuel supply pressure meets minimum requirements (typically 3-5 bar).

Step 5: Check for ECM Software Updates Contact a Kobelco dealer to verify if ECM calibration updates exist for your machine's serial number that address fuel pressure control logic, as early SK140 models received updates for improved pressure regulation algorithms.

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Disclaimer: This guide provides general troubleshooting information for Code 06568. High-pressure fuel systems operate at extreme pressures and require specialized tools and training. Always consult the official Kobelco service manual and consider professional diagnosis by a certified technician, especially when working on safety-critical fuel system components.