There may be a short in the relay between the door locks and the switch. First check the wiring between the locking mechanism and the switch, if that check out it may be a short in the fuse itself.
There are several things that can cause your Cadillac Deville to have transmission problems. The most common transmission problems are worn transmission gears.
Absolutely
dirt in the speed snsor bad speedo head in the dash
Heater coil
1 or more out of balance tires
A bad resistor or a bad switch.
One reason a 1998 Cadillac Deville would cut off while driving could be the fuel pump or the car is out of fuel. Another reason could be the spark plugs.
If the pedal is stuck down, no vacuum to the release diaphragm on the pedal
door button stuck --bulbs? fuse.
The blower control module is defective.
The DeVille could have low transmission. Or the internal transmission bands or valves could have failed. The transmission will most likely need a rebuild.
7.5 with filter! Previous answer is incorrect, if you put in 8 with filter change you will be half quart over and cause problems!