What is Sany SY245H Fault Code 20 (E320)?

Fault Code 20 (E320) on the Sany SY245H excavator indicates a Main Relief Valve Solenoid Circuit Malfunction or Hydraulic Pressure Sensor Electrical Fault. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal, open circuit, or short circuit in the wiring harness connected to the hydraulic system's pressure control components.

This code is critical because the main relief valve solenoid regulates maximum system pressure to prevent hydraulic component damage. When the ECM cannot properly communicate with or control this solenoid, the excavator may enter a protective derate mode or experience reduced hydraulic performance, directly impacting boom speed, swing function, and overall productivity on jobsites.

Common Symptoms

When Code 20 (E320) is active on your SY245H, operators typically experience:

• Amber hydraulic warning light illuminated on the instrument cluster
• Reduced hydraulic power across all functions (slow boom/arm movements)
• Intermittent loss of swing speed or jerky hydraulic operation
• Engine derate mode limiting RPM to protect the hydraulic system
• Error message displayed on the monitor panel indicating pressure system fault

Potential Causes

The most common technical causes for this fault code on used Sany excavators include:

• Damaged wiring harness near the main pump area where vibration causes insulation wear and exposed conductors
• Corroded electrical connectors at the solenoid valve due to water intrusion through worn cab floor seals
• Failed main relief valve solenoid (typically after 4,000-6,000 operating hours on used machines)
• Faulty hydraulic pressure sensor providing erratic voltage signals to the ECM
• ECM internal fault (less common) affecting the solenoid driver circuit
• Low battery voltage or poor ground connections causing inconsistent solenoid operation

How to Troubleshoot and Fix Code 20 (E320)

Step 1: Visual Inspection Begin by inspecting the wiring harness running from the ECM to the main control valve assembly. On used excavators, check specifically where the harness passes near the hydraulic tank and pump—this is a known rub point on SY245H models. Look for abraded insulation, pinched wires, or oil contamination on connectors.

Step 2: Electrical Testing Using a digital multimeter, disconnect the solenoid connector and measure resistance across the solenoid coil terminals. Sany specifications typically require 8-15 ohms resistance. Then check for voltage supply at the harness connector with ignition on—you should see approximately 12-14 volts. Test for shorts to ground by measuring resistance between each wire and chassis ground (should read infinite/open circuit).

Step 3: Connector and Sensor Inspection Remove and clean all electrical connectors with contact cleaner. Inspect pins for corrosion (common in high-humidity environments). On used machines, replace connector seals if rubber boots show cracking. Test the hydraulic pressure sensor by checking its voltage output at idle vs. high RPM using Sany diagnostic software or a compatible CAN bus scan tool.

Step 4: Component Replacement If testing reveals a failed solenoid (out-of-spec resistance) or sensor (erratic voltage), replace the faulty component with genuine Sany parts. Before installing, apply dielectric grease to connector pins to prevent future corrosion. After replacement, clear codes using diagnostic software and perform a hydraulic function test under load.

Critical Note for Used Equipment: Always inspect harness routing and secure any loose wiring with proper standoffs, as previous repairs may have altered factory harness placement, creating new wear points.

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Disclaimer: This guide provides general troubleshooting information. Hydraulic systems operate under extreme pressure and require specialized knowledge. Always consult a certified Sany technician or qualified heavy equipment mechanic for proper diagnosis and repair, especially when working with high-pressure hydraulic components.