Description & Operation: Notes

General Motors vehicles use a variety of vacuum and thermal operated switches, solenoids and valves to control the various emission systems. Some of the most commonly used of these are listed below. Some actual valve designs may vary from those shown. The chart can be used to identify and check operation of the various valves and switches. Emission Control Application Tables, located at the beginning of this manual, will help to determine component usage on specific engines. When calibration temperature has not been indicated, the temperature information may be found stamped on the base of the component.