What is Sany Excavator Fault Code P935?

Fault Code P935 indicates a malfunction in the hydraulic pump solenoid valve control circuit, specifically detecting an abnormal voltage or current signal that prevents proper hydraulic flow regulation. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an open circuit, short circuit, or incorrect resistance reading from the hydraulic pump's proportional solenoid valve wiring harness.

For Sany excavators, this code directly impacts the machine's ability to modulate hydraulic pressure and flow rates to the main pump. The proportional solenoid valve controls engine-pump matching, optimizing fuel efficiency and hydraulic power delivery. When P935 activates, the ECM typically enters a failsafe mode, limiting hydraulic performance to protect the system from potential damage. This fault is particularly critical in used excavators where electrical connections may have degraded over time.

Common Symptoms

• Reduced hydraulic power across all functions (boom, stick, bucket, swing), with noticeably slower cycle times
• Engine overspeed or hunting at idle as the ECM struggles to maintain proper engine-pump coordination
• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Intermittent loss of hydraulic response, especially when operating multiple functions simultaneously
• Increased fuel consumption due to loss of load-sensing capabilities and inefficient pump operation

Potential Causes

The most common technical causes for P935 in Sany excavators include:

• Damaged wiring harness between the ECM and hydraulic pump solenoid, particularly at known rub points near the pump mounting bracket and engine firewall
• Failed proportional solenoid valve due to internal coil breakdown or contaminated hydraulic oil causing mechanical sticking
• Corroded or loose electrical connectors at the solenoid valve plug, common in machines exposed to water or high-humidity environments
• ECM internal driver circuit failure, more prevalent in higher-hour used machines (8,000+ hours)
• Poor ground connection at the pump assembly or chassis grounding points
• Voltage supply issues from the main power distribution harness or battery system

How to Troubleshoot and Fix Code P935

Step 1: Visual Inspection Begin by thoroughly inspecting the wiring harness from the ECM to the hydraulic pump solenoid valve. Look for chafing, cuts, or burn marks, especially where the harness routes near hot engine components or sharp metal edges. Check all connector pins for corrosion, bent contacts, or moisture intrusion—common in used excavators.

Step 2: Electrical Testing Using a digital multimeter, disconnect the solenoid valve connector and measure resistance across the solenoid coil terminals. Typical specifications range from 8-15 ohms (consult your service manual). Next, check for supply voltage at the connector with the ignition on—you should see approximately 12-24V depending on your machine's electrical system. Verify ground continuity by measuring resistance between the solenoid ground pin and chassis ground (should be less than 1 ohm).

Step 3: Component Testing and Replacement If electrical values are within specification, connect Sany diagnostic software (PC Manager or equivalent) to read live data from the solenoid valve driver circuit. Monitor commanded versus actual current flow. Replace the proportional solenoid valve if readings are erratic or non-responsive. For used excavators, always inspect the valve's O-rings and sealing surfaces for hydraulic oil contamination that may indicate internal wear.

Step 4: Verify Repair After repairs, clear the fault code using diagnostic software, operate all hydraulic functions under load for 15-20 minutes, and recheck for code recurrence. Inspect all repair areas for proper harness routing and secure connections.

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Disclaimer: This guide provides general troubleshooting information for Sany excavator fault code P935. Hydraulic and electrical system diagnosis requires proper training and specialized tools. Always consult the manufacturer's service manual and consider professional assistance for complex repairs, especially on high-voltage systems.