What is Sany Excavator Fault Code P843?

Fault Code P843 indicates a malfunction in the hydraulic pump solenoid valve circuit, specifically detecting an abnormal voltage or current signal in the proportional control system. This diagnostic trouble code (DTC) is generated when the Electronic Control Module (ECM) detects an electrical fault in the hydraulic pump's proportional solenoid valve circuit, which regulates main pump displacement and flow.

This code is critical for Sany excavators because the proportional solenoid valve directly controls hydraulic pump output based on operator demand. When this circuit malfunctions, the ECM cannot properly modulate hydraulic flow, leading to reduced machine performance and potential component damage from improper pressure regulation.

Common Symptoms

When Code P843 is active on a Sany excavator, operators typically experience:

• Reduced hydraulic power across all functions (boom, arm, bucket, and swing operations become sluggish)
• Illuminated warning lamp on the instrument cluster, often accompanied by an audible alarm
• Engine derate mode where maximum RPM is limited to protect the hydraulic system
• Erratic hydraulic response with inconsistent cycle times or jerky movements
• Complete loss of hydraulic function in severe cases where the ECM enters failsafe mode

Potential Causes

The most common technical reasons for P843 on used Sany excavators include:

• Solenoid valve coil failure due to thermal stress or internal short/open circuit (resistance typically 8-12 ohms when functional)
• Damaged wiring harness from rubbing against the main pump housing or frame rails—a known wear point on older Sany models
• Corroded connectors at the pump solenoid or ECM interface, especially on machines with water exposure history
• ECM internal driver circuit failure affecting the proportional valve output channel
• Voltage supply issues from damaged power distribution circuits or poor grounding connections
• Contaminated hydraulic oil causing mechanical sticking of the solenoid spool valve

How to Troubleshoot and Fix Code P843

Step 1: Initial Diagnostic Scan Connect a Sany diagnostic software interface or compatible scan tool to retrieve freeze frame data. Document voltage readings and operating conditions when the fault occurred.

Step 2: Visual Inspection Inspect the solenoid valve wiring harness from the main hydraulic pump to the ECM. Check for abraded insulation, pinched wires near mounting brackets, and connector corrosion. On used excavators, carefully examine harness routing where it passes near the swing bearing—a common friction point.

Step 3: Electrical Testing Disconnect the solenoid valve connector and measure coil resistance using a digital multimeter. Specifications typically range from 8-12 ohms at 20°C. Test for continuity to ground (should show infinite resistance). Check supply voltage at the connector with ignition on—should read approximately 12V or 24V depending on system voltage.

Step 4: Signal Testing Using a breakout harness, monitor the ECM output signal to the solenoid while commanding pump functions through diagnostic software. The proportional signal should vary smoothly from approximately 0.5V to system voltage.

Step 5: Component Replacement If electrical values are out of specification, replace the faulty component. For used machines, always replace connector seals and apply dielectric grease to prevent future corrosion. Clear codes and perform operational testing under load.

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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.