Vacuum Switch?
 

When the code reader throws a code that says idle/decel vacuum switch is constantly closed, what does that mean and what vacuum switch is it talking about? :humm:

Year of the truck and engine

It is in my signature. 94 7.3 idi Turbo. Under that code, one line on the code reader says idle/decel vacuum switch is closed constantly and another line says wide open throttle vacuum switch closed constantly.