What is Sany Excavator Fault Code P190?

Fault Code P190 indicates a malfunction in the engine coolant temperature sensor circuit or an out-of-range temperature reading detected by the Engine Control Module (ECM). This code typically triggers when the ECM receives voltage signals from the coolant temperature sensor that fall outside the manufacturer's specified parameters (typically 0.5-4.5 volts), or when the sensor detects abnormally high or low coolant temperatures that may threaten engine integrity.

The coolant temperature sensor is critical for Sany excavators because the ECM relies on accurate temperature data to manage fuel injection timing, idle speed, engine warm-up cycles, and hydraulic oil temperature coordination. When this sensor circuit fails or provides erratic readings, the engine cannot optimize performance, potentially leading to reduced fuel efficiency, incomplete combustion, and accelerated component wear in used machines already experiencing normal degradation.

Common Symptoms

• Check Engine Light or warning indicator illuminated on the instrument panel, often accompanied by a coolant temperature gauge reading abnormally high, low, or fluctuating erratically
• Hard starting conditions, particularly during cold starts, as the ECM cannot properly enrich the fuel mixture without accurate temperature data
• Engine derate mode activation, limiting maximum RPM and hydraulic performance to protect the engine from potential overheating damage
• Rough idle or engine stalling during warm-up phases when the ECM relies heavily on temperature sensor input for fuel management
• Cooling fan running continuously at maximum speed, even when engine temperature appears normal

Potential Causes

• Faulty coolant temperature sensor due to internal element degradation, especially common in used excavators with 5,000+ operating hours
• Damaged or corroded wiring harness at connector points, particularly where the sensor harness runs near hot exhaust components or rubs against the engine block
• Corroded electrical connectors at the sensor plug or ECM interface, caused by coolant leaks or moisture intrusion in the engine compartment
• Open or short circuit in the sensor signal wire between the sensor and ECM, often found at harness flex points near engine mounts
• ECM internal fault (rare) affecting the temperature sensor circuit processing capability
• Low coolant level causing air pockets around the sensor, producing false high-temperature readings

How to Troubleshoot and Fix Code P190

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor location (typically mounted in the engine coolant outlet housing near the thermostat). Check coolant level first—low coolant creates air pockets that cause false readings. Examine the sensor wiring harness for visible damage, abrasion points, or melted insulation near hot engine surfaces. On used excavators, pay special attention to harness routing where it contacts frame members or passes through bulkheads, as vibration-induced wear is common. Inspect connector terminals for corrosion, bent pins, or coolant residue indicating gasket leaks.

Step 2: Electrical Testing Disconnect the coolant temperature sensor connector and use a digital multimeter to measure sensor resistance. At room temperature (68°F/20°C), resistance should typically read 2,000-3,000 ohms; consult Sany service specifications for exact values. Test sensor resistance while heating it in water with a thermometer—resistance should decrease smoothly as temperature rises. Check harness continuity from sensor connector to ECM using wiring diagrams. Measure voltage supply at the sensor connector with ignition on (engine off)—should read approximately 5 volts reference voltage from the ECM. A reading of 0V or 12V indicates harness or ECM issues.

Step 3: Component Replacement and Verification If sensor resistance values are out of specification or the sensor shows erratic readings during temperature changes, replace the coolant temperature sensor using OEM or quality aftermarket parts. Before installation, clean the sensor mounting bore and apply appropriate thread sealant to prevent coolant leaks. If harness testing revealed damaged wires or poor connections, repair or replace the affected harness section, ensuring proper routing away from heat sources and moving components—critical for used machines with original aging harnesses. After repairs, clear fault codes using Sany diagnostic software or a compatible scan tool, run the engine through complete warm-up cycles, and monitor for code recurrence while verifying proper temperature gauge operation.

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Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official Sany service manual for your specific excavator model and consider professional diagnostic assistance for complex electrical issues or if you lack proper testing equipment.