What is Sany Excavator Fault Code P905?

Fault Code P905 on Sany excavators indicates a malfunction in the hydraulic pump pressure sensor circuit or an abnormal pressure reading detected by the Engine Control Module (ECM). This code specifically relates to the main hydraulic pump's pressure monitoring system, which is critical for maintaining optimal hydraulic performance and protecting the machine from over-pressure or under-pressure conditions.

The hydraulic pump pressure sensor continuously monitors system pressure and sends voltage signals to the ECM. When the ECM detects voltage readings outside the predetermined range (typically 0.5-4.5V) or pressure values that don't correlate with actual operating conditions, it triggers P905. This fault is particularly critical for Sany excavators because the hydraulic system directly controls all work functions—boom, arm, bucket, and swing operations. Ignoring this code can lead to reduced machine performance, inefficient fuel consumption, or catastrophic hydraulic pump failure.

Common Symptoms

• Reduced hydraulic power across all functions, with noticeably slower cycle times for boom and arm movements
• Erratic hydraulic response or inconsistent pressure delivery during simultaneous multi-function operations
• Warning light illumination on the instrument cluster, often accompanied by a diagnostic trouble code display
• Engine derate mode activation, limiting RPM to protect the hydraulic system from damage
• Abnormal hydraulic pump noise or cavitation sounds indicating pressure regulation issues

Potential Causes

The most common technical causes for P905 in used Sany excavators include:

• Faulty hydraulic pump pressure sensor due to internal component degradation or contamination from hydraulic fluid breakdown
• Damaged wiring harness or corroded connectors between the sensor and ECM, especially at known rub points near the pump mounting area
• Low or contaminated hydraulic fluid causing inaccurate pressure readings or actual pressure fluctuations
• Failed ECM or internal ECM circuit issues preventing proper signal processing
• Hydraulic pump wear causing actual pressure loss that triggers legitimate fault detection
• Loose or damaged sensor mounting, allowing vibration-induced signal interference

How to Troubleshoot and Fix Code P905

Step 1: Visual Inspection Begin by inspecting the hydraulic pump pressure sensor location (typically mounted directly on the main pump body). Check for physical damage, oil contamination on connectors, or loose mounting bolts. On used excavators, examine the wiring harness routing from sensor to ECM for signs of chafing, especially where harnesses contact the frame or hydraulic lines.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across sensor terminals (consult Sany specifications, typically 200-3000 ohms depending on temperature). Test supply voltage at the harness connector with ignition on—should read approximately 5V. Check for continuity through the harness to the ECM and inspect for short circuits to ground.

Step 3: Hydraulic System Verification Check hydraulic fluid level and condition—contaminated or low fluid affects sensor accuracy. Install a calibrated pressure gauge at a test port to verify actual system pressure against sensor readings using Sany diagnostic software. Compare readings during various operations.

Step 4: Component Replacement If electrical tests pass but the code persists, replace the pressure sensor with OEM or quality aftermarket parts. For used machines, always apply dielectric grease to connectors to prevent future corrosion. If the sensor and wiring check good, ECM replacement may be necessary after confirming proper grounding.

Disclaimer: This guide provides general troubleshooting information. Always consult Sany service manuals and qualified technicians for machine-specific procedures. Hydraulic system work requires proper safety precautions and specialized tools.