The same problem with my Lincoln Town Car. When disassembled the transmission, it was evident that the reverse piston did not move, "valve body" can not reverse the piston to move. All valves tested by documentation. I can not understand the problem!
The transmission is messed up, try playing between neutral/reverse and drive, my old Hyundai excel did that and the transmission did a weird sound then went back OK, but not for long. Recommended to change it.
If the transmission has a drain plug in the pan, remove the plug, allow to drain for at least 1/2 hour, so that the torque converter will drain, replace the plug, add fluid, run engine, put transmission in drive, neutral, reverse, neutral, drive, repeat for about 5 minutes, check fluid level, top off if needed, repeat running in drive, neutral, reverse. If the transmission does not have a drain, you have to drop the pan, which is best done by a transmission shop.
it prevents you from starting the engine while the transmission is in either DRIVE or REVERSE
It tells the transmission computer what gear the driver has selected. ie: park, reverse, neutral, drive, low
P - Parking R - Reverse N - Neutral D - Drive 2 - High Drive With Gear 2 L or 1 - Low Drive
it will drive but when in reverse it wont move
There is no drive in a standard transmission car. In most cases you will have reverse, neutral, 1st gear, 2nd gear, 3rd gear, 4th gear, and 5th gear.
you have a problem in your torque converter or transmission pump
It a protection that way u won't damage the transmission
Brakes locked?
Could be a frozen clutch pack. Time for a transmission rebuild.
park,reverse,neutral,drive,low2,and low1