What is Sany Excavator Fault Code P874?

Fault Code P874 indicates a malfunction in the Engine Oil Pressure Sensor Circuit, specifically detecting an abnormally high voltage signal being sent to the Engine Control Module (ECM). This diagnostic trouble code (DTC) triggers when the ECM receives a voltage reading from the oil pressure sensor that exceeds the manufacturer's predetermined threshold, typically above 4.5-4.8 volts on Sany excavator systems.

The engine oil pressure sensor plays a critical role in monitoring lubrication system integrity by continuously measuring oil pressure and transmitting this data to the ECM. When the sensor circuit voltage reads abnormally high, the ECM cannot accurately determine actual oil pressure levels, potentially putting the engine at risk. For used Sany excavators, this code is particularly critical because inadequate oil pressure monitoring can lead to catastrophic engine damage, especially in machines with higher operating hours where internal wear may already be present.

Common Symptoms

• Engine warning light or check engine light illuminated on the instrument cluster
• Engine derate mode activated, limiting machine power output to 70-80% of normal capacity
• Oil pressure gauge reading maximum pressure continuously, regardless of actual engine conditions
• Intermittent alarm warnings accompanied by audible beeping from the cab display
• Potential engine shutdown in extreme cases where the ECM enters protective mode

Potential Causes

The most common technical causes for P874 on Sany excavators include:

• Damaged or corroded sensor wiring harness, particularly at flex points near the engine block where vibration causes insulation breakdown
• Failed engine oil pressure sensor with internal short circuit causing high voltage output
• Corroded or loose electrical connectors at the sensor or ECM connection points—extremely common in used machines exposed to moisture
• Chafed wiring rubbing against engine components, frame rails, or hydraulic lines creating intermittent short-to-voltage conditions
• ECM internal circuit failure (rare but possible in high-hour machines)
• Aftermarket sensor incompatibility if the sensor was previously replaced with non-OEM parts

How to Troubleshoot and Fix Code P874

Step 1: Visual Inspection Begin by conducting a thorough inspection of the oil pressure sensor and its wiring harness from the sensor to the ECM. Look specifically for damaged insulation, corrosion on connector pins, oil contamination on connectors, and physical damage. On used excavators, pay special attention to harness routing where cables may have rubbed against hot or moving components over thousands of operating hours.

Step 2: Electrical Testing Disconnect the oil pressure sensor connector and use a digital multimeter to check sensor resistance. A functioning sensor typically reads 50-250 ohms (consult Sany specifications). Next, with the ignition on but engine off, check the supply voltage at the harness connector—it should read approximately 5 volts. A reading above 5.2 volts indicates a potential wiring short-to-voltage condition.

Step 3: Circuit Continuity and Isolation Check for continuity between the signal wire and battery positive voltage—there should be infinite resistance (open circuit). If continuity exists, trace the harness to locate the short circuit. Inspect connector terminals for bent pins causing cross-connection and check for moisture intrusion, which is common in older machines.

Step 4: Component Replacement and Verification If wiring tests normal, replace the oil pressure sensor with an OEM-equivalent part. After replacement, clear the fault code using Sany diagnostic software or a compatible scan tool, then operate the machine under load to verify the repair. Monitor oil pressure readings during the test cycle to ensure proper sensor function.

---

Disclaimer: This guide provides general diagnostic information for Sany excavator fault code P874. Always consult the official Sany service manual for your specific model and consider engaging a certified heavy equipment technician for complex electrical diagnostics or if you're uncertain about any procedure.