Not sure what to call it but its a square plastic box about the size of your fist on the passenger side of the throttle body that has a round top on it.....it has three heater hoses going to it....mine cracked and it leaks coolant....somewhere in the GTA would be nice....you can call me at 905 668 6677...Doug

 

its this thing......a coolant by pass??

 

heater diverter valve . available at most any auto parts store , less than $20.00 . good luck .

 

my local jobber didnt have one but they are still available from the GM dealer $38.....thanks bud!...I never would have thought you could get that new

 

your welcome , GM used the same valve on many cars . good luck .