Staff Answer
Jul 20, 2026 - 06:42 PM
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The P0128 code indicates the engine is not reaching operating temperature fast enough, usually because the thermostat is stuck open.
Method 1: Inspect Coolant & Sensor
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Check Coolant Level: Ensure the coolant reservoir is at the proper level when cold. Low coolant leads to inaccurate temperature sensor readings.
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Check ECT Sensor: Use an OBD-II scanner to monitor live "ECT" (Engine Coolant Temperature) data. If the engine is hot but the sensor reports a low temperature, replace the faulty sensor.
Method 2: Replace Thermostat
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Removal: Locate the thermostat housing (usually connected to the lower radiator hose). Drain the coolant, remove the housing bolts, and swap the old thermostat for a new one.
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Bleed System: Install a new gasket, refill the cooling system, and properly bleed air from the lines to ensure accurate flow.
Warning: Never open a radiator cap while the engine is hot. Use genuine Nissan/OEM thermostats to ensure the opening temperature matches factory specifications.
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