What is Sany General Fault Code P150?

Sany fault code P150 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading exceeding normal operating parameters. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects either an electrical fault in the sensor circuit (open circuit, short circuit, or high resistance) or receives a temperature reading outside the programmed threshold values—typically above 105-110°C (221-230°F).

The coolant temperature sensor is critical for Sany excavators because it directly influences fuel injection timing, engine protection protocols, and hydraulic oil temperature management. When this sensor fails or provides inaccurate data, the ECM cannot properly regulate engine performance, potentially leading to overheating, reduced power output, or automatic engine derate to prevent catastrophic damage.

Common Symptoms

• Engine warning light illuminated on the instrument cluster, often accompanied by a high-temperature warning icon
• Engine derate mode activated, limiting RPM to 1200-1500 and reducing hydraulic flow by 30-40%
• Cooling fan running continuously at maximum speed, even during cold starts or low ambient temperatures
• Difficulty starting the engine or extended cranking time due to incorrect fuel mapping
• Erratic temperature gauge readings, fluctuating rapidly or showing maximum temperature immediately after startup

Potential Causes

In used Sany excavators, P150 typically results from age-related component degradation. The most common causes include:

• Coolant temperature sensor failure due to internal element corrosion or thermal cycling damage (common after 5,000+ operating hours)
• Wiring harness damage near the thermostat housing where cables experience heat stress and vibration friction
• Corroded or loose connector pins at the sensor plug, especially on machines operated in coastal or high-humidity environments
• ECM voltage supply issues providing incorrect reference voltage (should be 5.0V ±0.25V)
• Actual engine overheating caused by coolant system failures (low coolant level, failed thermostat, clogged radiator)
• ECM software glitches or corrupted calibration files in older control modules

How to Troubleshoot and Fix Code P150

Step 1: Visual Inspection and Data Verification Connect a diagnostic scanner (Sany PC-E or compatible J1939 tool) to retrieve freeze frame data showing the exact temperature reading when P150 triggered. Physically inspect the coolant temperature sensor (located near the thermostat housing on the cylinder head) for physical damage, coolant leaks, or connector corrosion. Check actual coolant level and condition—contaminated or low coolant can cause genuine overheating.

Step 2: Electrical Circuit Testing Disconnect the sensor connector and measure reference voltage at the harness side—it should read 4.75-5.25V with ignition on. Using a digital multimeter, check sensor resistance: at 20°C (68°F), resistance should be approximately 2,200-2,800 ohms; at 80°C (176°F), approximately 280-320 ohms. Values outside this range indicate sensor failure. Inspect the wiring harness for abraded insulation, especially where it contacts the engine block or routing brackets common wear points on used machines.

Step 3: Component Replacement and System Reset If electrical values are correct but the code persists, test the ECM ground circuits (should have less than 0.5 ohms resistance to chassis ground). Replace the coolant temperature sensor using OEM or equivalent parts (aftermarket sensors often have incorrect resistance curves). After replacement, clear fault codes, perform a cold-start test cycle, and monitor live data to confirm temperature readings climb gradually (approximately 2-3°C per minute). For used excavators with 8,000+ hours, consider replacing the entire sensor-to-ECM harness section to eliminate hidden internal wire damage.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Sany service manual for your specific model and serial number. If unfamiliar with electrical diagnostics or high-temperature engine systems, seek assistance from a certified heavy equipment technician to prevent injury or further machine damage.