What is Yanmar General Fault Code P1568?

Fault Code P1568 indicates a malfunction in the Exhaust Gas Recirculation (EGR) valve control circuit or an abnormal EGR valve position signal detected by the Engine Control Module (ECM). This code typically appears when the ECM receives voltage readings outside the expected range from the EGR position sensor, or when the valve fails to respond correctly to commanded positions.

The EGR system on Yanmar diesel engines recirculates a portion of exhaust gases back into the intake manifold to reduce combustion temperatures and lower NOx emissions. When P1568 triggers, the ECM cannot accurately control or verify the EGR valve position, directly impacting emissions compliance and engine performance. For used excavators, this fault often results from accumulated carbon deposits, worn electrical connections, or sensor degradation over thousands of operating hours.

Common Symptoms

• Engine warning light illuminated on the instrument cluster, often accompanied by reduced power output
• Rough idle or unstable engine speed, particularly noticeable during warm-up periods
• Black smoke from the exhaust during acceleration due to improper air-fuel mixture
• Engine derate mode activated, limiting machine performance to protect the engine from potential damage
• Increased fuel consumption as the ECM defaults to open-loop operation without proper EGR feedback

Potential Causes

The most common causes of P1568 on used Yanmar excavators include:

• Failed or contaminated EGR position sensor due to carbon buildup or internal component wear
• Damaged wiring harness at known rub points near the EGR valve mounting location, especially where cables contact engine brackets
• Corroded or loose electrical connectors on the EGR valve or position sensor from moisture intrusion
• Mechanical EGR valve failure, including stuck valve stems from carbon accumulation or broken return springs
• ECM software issues or corrupted calibration files (less common but possible in older machines)
• Vacuum line leaks or failed solenoids in vacuum-actuated EGR systems

How to Troubleshoot and Fix Code P1568

Step 1: Visual Inspection and Connector Check Begin by inspecting the EGR valve and its wiring harness for obvious damage, corrosion, or oil contamination. On used excavators, pay special attention to connector terminals—clean them with electrical contact cleaner and check for bent pins. Inspect harness routing for wear points against engine components or frame members.

Step 2: Electrical Testing with Diagnostic Tools Using a digital multimeter, check the EGR position sensor supply voltage (typically 5V reference from the ECM) and ground continuity. Test sensor signal voltage throughout the valve's range of motion—readings should change smoothly between approximately 0.5V and 4.5V. Consult Yanmar diagnostic software or a factory service manual for exact specifications for your engine model.

Step 3: Mechanical Valve Inspection Remove the EGR valve and physically inspect for carbon buildup restricting movement. Clean the valve and intake passages with appropriate EGR cleaner. Test valve operation manually—it should move freely without binding. If the valve stem is seized or damaged, replacement is necessary.

Step 4: Sensor Replacement and Verification If electrical tests reveal sensor failure, replace the EGR position sensor with OEM or high-quality aftermarket parts. After replacement, clear fault codes using diagnostic software and perform a relearn procedure if required by the manufacturer.

Step 5: Road Test and Monitor Operate the excavator under normal working conditions while monitoring live data through the diagnostic interface. Verify that EGR valve position matches commanded values and that no codes return.

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Disclaimer: This guide provides general troubleshooting information for Yanmar fault code P1568. Always consult the manufacturer's service manual for your specific machine model and serial number. If you're unfamiliar with diesel engine diagnostics or electrical systems, seek assistance from a qualified heavy equipment technician to avoid costly mistakes or safety hazards.