What happens when someone defaults on a car loan?

Technically I know what happens. My question surrounds my son. He purchased a vehicle and used old information to obtain the loan. This is the first loan he got with a co-signer. He "bought" the car in April and has not made a payment yet. He did go to the bank and talked to them last week and he is to pay $200 a paycheck to catch up payment in addition to monthly payment. We know he is not going to be able to do this so what will happen and how quickly?