The stock oil pan for the engine or diesel do not appear to have two drain plugs. So do you have the stock oil pan or another one? Either way the reason you have two plugs is for one of two reasons. First it is the design of the pan that it may have a dual sump or baffle so you need to drain both sides to get all the oil out. The other reason is, some aftermarket pans put two in it for convenience and speed of drain oil. Basically an attempt at making a "better mousetrap."
However, if this other drain plug is in the side of the pan then that is the location of the oil level sensor. I attached info below on this. Let me know if this is it or can you get pictures of the pan for us to look at? Thanks
Image (Click to make bigger)
Monday, February 22nd, 2021 AT 3:13 PM