What is Sany Excavator Fault Code E451(51)?

Fault Code E451(51) indicates a malfunction in the hydraulic pump solenoid valve circuit or an abnormal current signal detected by the Electronic Control Unit (ECU). This code specifically relates to the proportional solenoid valve that regulates hydraulic pump displacement and system pressure in Sany excavators.

The ECU continuously monitors the electrical current flowing through the hydraulic pump solenoid valve. When the current falls outside the manufacturer's specified range (typically due to open circuits, short circuits, or internal solenoid failures), the system triggers E451(51). This fault is critical because the hydraulic pump is the heart of excavator operation—controlling boom, arm, bucket, and swing functions. Any disruption to the solenoid valve circuit can result in reduced machine performance or complete hydraulic system failure.

Common Symptoms

• Reduced hydraulic power across all functions, with noticeably slower cycle times for boom, arm, and bucket operations
• Engine RPM fluctuations or failure to reach maximum rated speed under load
• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Hydraulic system operating in derate mode, limiting pump output to protect components
• Intermittent loss of hydraulic functions, particularly during cold starts or after extended operation

Potential Causes

The most common technical reasons for E451(51) in used Sany excavators include:

• Damaged wiring harness between the ECU and hydraulic pump solenoid, particularly at flex points near the engine mount or pump assembly where vibration causes wire chafing
• Failed proportional solenoid valve due to internal coil burnout, contamination from dirty hydraulic oil, or normal wear in high-hour machines
• Corroded or loose electrical connectors at the solenoid valve or ECU, especially in machines exposed to wet conditions
• ECU internal faults or software corruption, more common in older model controllers
• Voltage supply issues from the main power harness, battery connections, or alternator output irregularities

How to Troubleshoot and Fix Code E451(51)

Step 1: Connect a Sany diagnostic tool or compatible OBD reader to retrieve freeze frame data. Record the operating conditions when the fault occurred (engine temperature, hours, load).

Step 2: Perform a visual inspection of the solenoid valve wiring harness. On used excavators, pay special attention to areas where the harness passes through metal brackets or rubs against the engine block. Look for abraded insulation, exposed copper, or heat damage.

Step 3: Disconnect the solenoid valve connector and inspect for corrosion, bent pins, or moisture intrusion. Clean contacts with electrical contact cleaner and dielectric grease.

Step 4: Using a digital multimeter, measure the solenoid coil resistance at the valve connector (typically 3-8 ohms for Sany proportional valves). Compare readings to manufacturer specifications in the service manual.

Step 5: Check supply voltage at the solenoid connector with the ignition on (should read 12-24V depending on machine voltage). If voltage is absent, trace the circuit back to the ECU and check fuses and relays.

Step 6: If resistance and voltage are within specification, the ECU may require reprogramming or replacement. Before replacing the ECU on used machines, verify all ground connections are clean and tight, as poor grounds often mimic ECU failures.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sany service manual for your specific model and serial number. Complex electrical diagnostics should be performed by qualified technicians with proper training and equipment.