The theory that all credit is good credit is junk science. If you are in need of a second chance auto loan, you already know how credit can turn on you. One belief holds true, though. Credit cards can be a gateway to an approved auto loan.
A credit card will prove your ability to handle a revolving credit balance in a responsible manner or it will show that you are living week to week and need every penny available to make it through the month. If you have a credit card that is maxed out, you are barely making the monthly minimum payments, and immediately use all available credit, your credit score will suffer.
On the other hand, you can show credit responsibility by only applying for a small number of cards. Once you have one or two cards, do not hold a balance that exceeds 25-30% of your available credit limit. On time monthly payments reflect well on your credit score, but carrying a high percentage of your credit limit as a balance reflects negatively. The two will not balance, as the high balance reflects more heavily than the on time payments.
Even if you need to obtain a secured credit card, you will be more readily approved for a second chance car loan if you have a positive experience with revolving credit. Remember to mind your balance as well as make your payments on time.