Monitor Description

WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.

The resistance of the engine coolant temperature sensor varies in proportion to the actual engine coolant temperature The ECM supplies a constant voltage to the sensor and monitors the signal output voltage of the sensor The signal voltage output varies according to the changing resistance of the sensor. After the engine is started, the engine coolant temperature is monitored through this signal If the engine coolant temperature sensor indicates that the engine is not yet warm enough for closed loop fuel control, despite a specified period of time having elapsed since the engine was started, the ECM interprets this as a malfunction in the sensor or cooling system and sets the DTC

Example

The engine coolant temperature is 0°C (32°F) at engine start After about 1 minute running time, the engine coolant temperature sensor still indicates that the engine is not warm enough to begin closed loop fuel (air fuel ratio feedback) control The ECM interprets this as a malfunction in the sensor or cooling system and sets the DTC