Q: I have a 2004 Chevy impala that doesn't move when it's in drive an i step on the gas peddle. Why?

This may be a number of different possibilities, however it sounds like it may be related to a transmission problem. This can happen for a few different reasons such as low transmission fluid or a faulty control solenoid. An automatic transmission requires hydraulic pressure generated by the transmission fluid that gets pushed through a series of chambers inside the transmission, activating solenoids that cause the transmission to shift at specific intervals. These intervals are controlled by the transmission control module which reads input from transmission speed sensors to determine the rotational speed of the input and output shafts in the transmission. Based upon this information, the control module directs the transmission shifting function. When any of these components are not working properly, you may notice an erratic shifting of gears or in some cases the transmission may not shift at all. I would suggest having a professional from YourMechanic come to your location to take a look at your vehicle.