My LX 176 shuts down as soon as I release the brake the mower was working great then shut down like a sensor went bad. What sensor would be bad to cause this problem and also where would it be located?

That shut down switch is one of 3-4 kill switches. It thinks you are doing something unsafe and they do go bad. The most ferequently failing kill switch is under your fanny but this switch should be found on the brake linkage. Open the hood and have someone release and engage the brake over and over as you observe the action of the linkage, you should see a switch with two wires comiong off it.

Hi,
I agree with the seat switch part of the answer. The LX models often had a seat switch mounted externally under the left side of the seat on a weak bracket that was subject to rust, corrosion and breakage. Check there first.
Peace,
Clarke