What is Sany General Fault Code P737?

Fault Code P737 indicates a malfunction in the hydraulic pump pressure sensor circuit, specifically detecting an abnormal voltage signal or pressure reading outside the manufacturer's specified range. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) receives sensor data that falls below the minimum threshold or exceeds the maximum allowable voltage, typically outside the 0.5-4.5V range standard for analog pressure sensors.

In Sany excavators, the hydraulic pump pressure sensor plays a critical role in monitoring system pressure to optimize fuel efficiency, prevent component damage, and ensure proper load-sensing hydraulic function. When this sensor fails or provides erratic signals, the ECM cannot accurately regulate pump output, potentially leading to reduced machine performance, increased fuel consumption, or activation of protective derate modes that limit operational capabilities.

Common Symptoms

• Amber warning light illuminated on the instrument cluster with reduced hydraulic power during digging or lifting operations
• Intermittent or complete loss of hydraulic responsiveness, particularly noticeable during high-demand tasks
• Engine derate mode activation, limiting RPM to protect the hydraulic system from damage
• Erratic boom, arm, or bucket movements that feel sluggish or unresponsive to joystick inputs
• Increased fuel consumption due to improper pump compensation and inefficient hydraulic flow management

Potential Causes

The most common technical causes for P737 in used Sany excavators include:

• Pressure sensor internal failure due to seal degradation, membrane damage, or electrical component breakdown from extended use
• Corroded or loose electrical connectors at the sensor harness connection point, especially on machines exposed to harsh environments
• Wiring harness damage from rubbing against hydraulic lines or frame components near the pump assembly—a known wear point on older Sany models
• Contaminated hydraulic oil causing sensor port blockage or membrane coating that affects pressure reading accuracy
• ECM voltage supply issues providing incorrect reference voltage to the sensor (typically should be 5V ±0.25V)
• Damaged pins or moisture intrusion in the sensor connector causing short circuits or open circuits

How to Troubleshoot and Fix Code P737

Step 1: Visual Inspection and Connector Check Begin by inspecting the pressure sensor located on the main hydraulic pump assembly. Check the electrical connector for corrosion, bent pins, or moisture. On used excavators, pay special attention to the wiring harness routing—look for signs of chafing, melted insulation, or previous repair attempts with electrical tape. Clean connectors with electrical contact cleaner and ensure secure connection.

Step 2: Electrical Testing with Multimeter Disconnect the sensor and measure the supply voltage at the harness connector with the ignition on—you should read approximately 5 volts. Next, check sensor resistance (typically 200-500 ohms depending on temperature) and output voltage signal while engine is running. Compare readings against Sany specifications. If voltage is absent or incorrect, trace the harness back to the ECM for breaks or shorts.

Step 3: Sensor Replacement and System Verification If electrical tests confirm sensor failure, replace with a genuine or OEM-equivalent hydraulic pressure sensor. Before installation on used machines, inspect the sensor mounting port for debris, metal shavings, or hydraulic fluid contamination. After replacement, clear the fault code using Sany diagnostic software or a compatible scan tool, then perform a function test under load to verify proper hydraulic response and confirm the code does not return.

Disclaimer: This guide provides general troubleshooting information. Hydraulic system repairs can be complex and potentially dangerous. Always consult your Sany service manual and consider professional diagnostic assistance, especially when working with high-pressure hydraulic systems on used equipment with unknown maintenance history.