What is Sany Excavator Fault Code P805?

Fault Code P805 on Sany excavators indicates a Main Relief Valve Solenoid Circuit Malfunction or abnormal electrical signal detected in the hydraulic system's pressure control circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an open circuit, short circuit, or out-of-range voltage in the wiring or solenoid that controls the main relief valve. This valve is critical for regulating maximum system pressure in the hydraulic circuit, preventing damage to pumps, cylinders, and hoses.

For Sany machines, this code directly impacts operational safety and efficiency. When P805 appears, the ECM may default to a reduced power mode to protect hydraulic components from overpressure or erratic pressure fluctuations, significantly affecting digging force and cycle times.

Common Symptoms

When Code P805 is active, operators typically experience:

• Warning light illuminated on the instrument cluster, often accompanied by a hydraulic system alert
• Reduced hydraulic power or sluggish boom/arm/bucket movements
• Erratic hydraulic response during operation, with inconsistent digging force
• Engine derate mode engaged, limiting RPM to prevent system damage
• Intermittent loss of auxiliary hydraulic functions

Potential Causes

The most common technical reasons for P805 on used Sany excavators include:

• Faulty main relief valve solenoid due to internal coil failure or mechanical wear
• Damaged wiring harness between the ECM and solenoid, especially at flex points near the pump or valve bank
• Corroded or loose electrical connectors at the solenoid or ECM (common in machines with high hour counts)
• Short to ground caused by harness chafing against the frame or hydraulic lines
• ECM internal fault or software calibration issue (less common but possible in older units)
• Low battery voltage or poor ground connections affecting solenoid actuation

How to Troubleshoot and Fix Code P805

Step 1: Visual Inspection
Inspect the main relief valve solenoid and its wiring harness for obvious damage, corrosion, or oil contamination. On used excavators, check harness routing near the hydraulic pump and valve block for wear points where insulation may have rubbed through.

Step 2: Electrical Testing
Using a digital multimeter, measure solenoid resistance (typically 10-30 ohms for Sany solenoids). Disconnect the connector and check for continuity and short to ground. Verify supply voltage at the connector (usually 12-24V depending on model) with ignition on.

Step 3: Connector and Ground Verification
Clean all connector pins with electrical contact cleaner and check for bent terminals. Verify ground circuit continuity from the solenoid back to the ECM and chassis ground. Poor grounds are extremely common in high-hour used machines.

Step 4: Solenoid and Harness Replacement
If testing confirms solenoid failure, replace with OEM or quality aftermarket parts. If wiring is compromised, repair or replace the affected harness section, ensuring proper routing away from heat and abrasion points.

Step 5: Clear Code and Test
Use Sany diagnostic software or a compatible scan tool to clear the fault code. Operate the machine under load and monitor for code recurrence.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Sany service manual for your specific model and consider professional diagnostic assistance for complex electrical or hydraulic issues.