The DTC code P0546 OBDII refers to the EGT (Exhaust Gas Temperature) Sensor located in the pipe, in front of the Catalytic Converter (TWC). The purpose of this sensor is to protect the converter from excessive heat.
The resistance of the sensor is sensitive to heat. It converts the exhaust temperature into an electrical signal, which is sent to the vehicle’s computer. The higher the temperature in the exhaust, the lower the resistance to the ground, resulting in a high voltage. If the temperature drops, the resistance increases, and the voltage are lower. When the engine detects a high voltage, the PCM (Powertrain Control Module) is responsible for changing the engine timing or fuel ratio to keep the temperature in acceptable ranges within the TWC (Catalytic Converter).
If the voltage sent to the PCM exceeds the limits already set by the vehicle manufacturer, this code is stored and the Check Engine light will illuminate.