Catalytic Converter And Over-Temperature Control System: Operation: Notes

Catalytic converter oxidizes exhaust gases into harmless non-polluting gases. The over-temperature control system components work as follows:

While coasting, coasting fuel cut device is engaged to prevent rich mixtures from reaching converter.
When converter reaches about 1350°F (730°C), due to high load conditions, air pump system air is diverted to atmosphere via action of the air switching valve and vacuum switching valve. This helps reduce chemical reaction in catalyst, which would create even higher temperatures.
Above 1830°F (1000°C), warning lamp and buzzer will be activated, indicating an over-temperature condition. Such may be caused by misfiring engine.

NOTE: Buzzer will automatically stop when catalyst temperature returns to normal. Warning light will not turn off until battery positive cable is disconnected and reconnected.

Fig 1: Catalytic Converter and Over-Temperature Control System (California Only)

Courtesy of GENERAL MOTORS COMPANY