Leaking heater core.
If you are talking about a 2000-2005 Cadillac Deville DHS and DTS it would be just a trim level. DHS stands for Deville High Luxury Sedan and DTS stands for Deville Touring Sedan. The DHS had some extra luxury features the DTS did not, but the DTS was still a more pricey trim level with a higher output Northstar V8, 17 inch wheels, floor shifter, bucket seats and a firmer ride. All things the DHS trim or standard Deville trim did not have.
Heater core has failed.
most 90s caddies have the spare tire in the trunk under panel in the floor.
According to the Honda Floor Mats website, there are four different floor color mats available for the Honda Civic Sedan. The colors that are available are grey, black, brown and beige.
Floor mats for Cadillac vehicles can be purchased from Cadillac dealers. They can also be found at department stores with an automotive section such as Sears, stores that sell auto parts and accesories, and on Amazon.
Yes vents can be in the floor instead of the wall.
Look for switch on floor
I am assuming that you want to know where the Catalytic converter is in your 1990 Cadillac. it is underneath the car, silver color (or rust) welded to the exhaust pipe about the center of the front seat floor.
Cadillac car mats can be purchased when you go to a store called CariD. This store sells auto accessories like car floor mats for many brands and makes of cars, Cadillac included.
Inside the fuel tank, To get to the fuel pump you must remove the back seat on the sedan or if it is a wagon remove the carpet on the back floor-same on a sedan, There will be an oval plate- remove it , The fuel pump is right there.