What if the owner of the car passed away and the co signer is still living can the co signer change it to their name?

Co signing a loan does not provide any ownership rights. If the title is in the name of the decedent the ownership will pass to their heirs under their will or under the laws of intestacy. You may be able to obtain a court order if there is a balance on the loan and you have proof that you made payments. You may need to buy it from the heirs, if any. You should consult with an attorney who specializes in probate.