What is Sany General Fault Code P118?

Fault Code P118 on Sany excavators indicates a malfunction in the hydraulic pump pressure sensor circuit, specifically detecting an abnormally high voltage signal or open circuit condition. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) receives a voltage reading from the hydraulic pump pressure sensor that exceeds the manufacturer's specified threshold, typically above 4.8 volts on a 5-volt reference circuit.

This fault is critical for Sany excavators because the hydraulic pump pressure sensor provides real-time feedback to the ECM, enabling precise control of hydraulic flow and system pressure. When P118 activates, the machine may enter a derate mode to protect hydraulic components from potential damage, significantly impacting productivity and operational efficiency on job sites.

Common Symptoms

• Hydraulic system warning light illuminated on the instrument cluster, often accompanied by an audible alarm
• Reduced hydraulic performance including slower boom, arm, or bucket movements due to system derate
• Erratic hydraulic response where implements may respond inconsistently to joystick commands
• Engine power limitation as the ECM restricts output to protect the hydraulic system
• Intermittent fault activation especially during cold starts or after extended idle periods on used machines

Potential Causes

The most common technical causes for P118 on used Sany excavators include:

• Failed hydraulic pump pressure sensor due to internal component degradation or diaphragm rupture
• Damaged sensor wiring harness particularly at known rub points near the hydraulic pump mounting area where vibration causes wire insulation breakdown
• Corroded or loose electrical connectors at the sensor or ECM interface, especially on machines operating in wet or corrosive environments
• Open circuit conditions caused by broken wires within the harness bundle running from the pump to the main controller
• ECM internal fault affecting the 5-volt reference voltage supply circuit (less common but possible on high-hour machines)
• Aftermarket sensor incompatibility if previous repairs used non-OEM components with incorrect resistance specifications

How to Troubleshoot and Fix Code P118

Step 1: Visual Inspection and Connector Check Begin diagnostics by locating the hydraulic pump pressure sensor mounted on the main hydraulic pump assembly. Disconnect the sensor connector and thoroughly inspect both the sensor pins and harness connector for corrosion, bent pins, or moisture intrusion. On used excavators, pay special attention to connector seal integrity as environmental contamination is a frequent cause. Clean connectors with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Sensor Circuit Testing Using a digital multimeter (DMM), perform voltage and resistance checks. With the ignition on and sensor disconnected, measure voltage at the harness connector. You should find approximately 5 volts on the reference wire and 0 volts (ground) on the signal return wire. If voltage readings are incorrect, trace the harness for shorts to power, shorts to ground, or open circuits. Check harness routing near hydraulic lines and frame members where abrasion commonly occurs on aging machines.

Step 3: Sensor Resistance and Replacement Measure the sensor's internal resistance according to Sany specifications (typically 200-5000 ohms depending on temperature). Compare readings to factory specifications using Sany diagnostic software if available. If resistance is out of specification or reads infinite (open circuit), replace the sensor with an OEM Sany pressure sensor to ensure proper calibration. Before installing a new sensor, inspect the sensor mounting port for metal debris or hydraulic fluid contamination that could affect readings.

Step 4: Harness and ECM Verification If the sensor and immediate wiring test correctly, inspect the complete harness route from sensor to ECM, checking for wire damage at cable ties, through bulkhead connectors, and at the ECM connector itself. For persistent faults on used equipment, consider harness continuity testing wire-by-wire. If all wiring proves sound, the ECM's sensor input circuit may require professional diagnosis with factory-level diagnostic equipment.

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Disclaimer: This guide provides general troubleshooting information for Sany excavator fault code P118. Hydraulic and electrical system diagnostics should be performed by qualified heavy equipment technicians with appropriate training and tools. Always consult the official Sany service manual for your specific model and serial number, and follow proper lockout/tagout procedures when working on heavy equipment.