Exhaust Temperature Sensor: Description and Operation

Air Injection System (AIS):

Heat Hazard Sensor Warning Light:

The heat hazard sensor is located in the vehicle floor above the catalytic converter. If floor temperature reaches a potentially dangerous level because of converter overheating, a warning light illuminates on the dash and the sensor signals the ECU. To cool the converter and diminish the hazard, the ECU directs the secondary air control valve to curtail airflow to the converter. To accomplish this, the ECU directs vacuum to the relief valve diaphragm of the air control valve by energizing the relief solenoid valve.