What is Sany General Fault Code P620?

Fault Code P620 on Sany excavators indicates a Hydraulic Pump Pressure Sensor Circuit Malfunction or Abnormal Signal from the Main Pump Pressure Sensor. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects voltage readings outside the acceptable range from the pressure sensor monitoring the main hydraulic pump's discharge pressure.

This code is critical because the hydraulic pump pressure sensor provides real-time feedback to the ECM, which adjusts engine speed, pump displacement, and overall hydraulic flow to match operational demands. When the ECM cannot accurately read hydraulic pressure, it may limit machine performance to prevent damage, resulting in reduced digging force, slower cycle times, or complete hydraulic system derate. On used Sany excavators, this fault often stems from sensor degradation, wiring harness damage from vibration and heat exposure, or connector corrosion—common issues in machines with extensive operating hours.

Common Symptoms

• Hydraulic power loss or noticeably reduced digging and lifting force
• Engine derate mode activation, limiting RPM to protect the hydraulic system
• Warning light illuminated on the instrument cluster, possibly accompanied by audible alarms
• Erratic hydraulic response, such as jerky or inconsistent boom/arm movements
• Intermittent fault code appearance, especially during high-load operations or after machine warm-up

Potential Causes

• Faulty hydraulic pump pressure sensor due to internal component wear or diaphragm failure
• Damaged wiring harness near the pump area where cables experience heat, vibration, and hydraulic fluid exposure
• Corroded or loose electrical connectors at the sensor or ECM, particularly common in used machines exposed to moisture
• Short circuit or open circuit in the sensor signal wire caused by chafing against metal surfaces
• ECM internal fault (less common) affecting the sensor input circuit
• Contaminated hydraulic fluid causing sensor membrane blockage or erratic readings

How to Troubleshoot and Fix Code P620

Step 1: Visual Inspection Begin by inspecting the hydraulic pump pressure sensor (typically mounted on the main pump housing). Check for physical damage, oil leaks, and secure mounting. Examine the wiring harness from the sensor to the ECM for visible wear, chafing points, or heat damage—common in used excavators with 5,000+ hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals (consult Sany service manual for specification, typically 200-500 ohms). Check supply voltage at the connector with ignition on (should read approximately 5V reference voltage). Inspect for continuity in signal and ground wires back to the ECM.

Step 3: Connector and Harness Assessment On used machines, carefully clean all connector pins with electrical contact cleaner and inspect for corrosion or bent terminals. Check for intermittent connections by gently wiggling the harness while monitoring live data with Sany diagnostic software or compatible scan tool.

Step 4: Component Replacement If electrical tests confirm sensor failure, replace the hydraulic pump pressure sensor with OEM or quality aftermarket parts. After replacement, clear codes, perform a calibration procedure if required, and test under load conditions.

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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 system repairs.