If a party fails to make a child support payment when due, each unpaid obligation becomes an enforceable judgment automatically by law. C.R.S. 14-10-122(1)(c). Therefore, if you owe arrears, you have an enforceable judgment against you which can be used to collect including garnishing wages, placing a lien on property, and/or repossessing property. It's not clear if you are making payments on the vehicle or the child support arrears. If it is the vehicle - the fact that you are making payments on the vehicle is irrelevant to whether or not it can be repossessed. If you are making payments on your child support arrears - if you have an agreement regarding satisfaction of the arrears through a payment plan, the recipient cannot take other action against you. However, if you do not have an agreement, it is as stated above, they have an enforceable judgment against you. I would suggest you discuss with an attorney to better understand your obligations and rights and to protect your property going forward.