So I just went under the car and saw it had disc brakes on the rear end and i wrote down the code on the axle which is 3pz c221 2 can't find much information any info would be greatly appreciated thank you.

 

Change the fluid.

While doing so, LOOK AT the parts. You will find out more that way than you EVER will with "codes"; and you will be able to have ABSOLUTE CERTAINTY that you not only have correctly identified what parts you have, but also, you will have taken care of one of the most common "deferred maintenance" items people let slip on their cars.