Monitor Description

WARNING: This page is about a different car, the 2025 Lexus RX 350, 2024 Lexus RX 350, and 2023 Lexus RX 350. However, it is still accessible from the selected car via links, so may be relevant.

The engine coolant temperature sensor (for cylinder head side) is used to monitor the cylinder head side engine coolant temperature. The engine coolant temperature sensor (for cylinder head side) has a thermistor with a resistance that varies according to the temperature of the engine coolant. When the engine coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance decreases. These variations in resistance are reflected in the output voltage from the sensor. The ECM monitors the sensor voltage and uses this value to calculate the engine coolant temperature. If the engine coolant temperature sensor (for cylinder head side) output voltage deviates from the normal operating range, the ECM interprets this as a malfunction in the engine coolant temperature sensor (for cylinder head side) circuit, illuminates the MIL and stores a DTC.

Example:

If the engine coolant temperature sensor (for cylinder head side) output voltage is less than 0.081 V for 3 seconds or more, the ECM will illuminate the MIL and store this DTC.