Absolutely not. Lenders working in this space often are specialists meaning they only lend to people with adverse credit. This means they have seen everything and heard every story.
WARNING: If you read this website, your chances of getting car finance with bad credit will dramatically improve.
The number one thing you need to be is honest. If you can be as open as possible with the lender it will dramatically improve your chances of being approved.
All applications in this space are approved or declined by real people. They understand that from time to time people experience financial difficulty and they are willing to lend you money. BUT and its a big BUT, if they find something that illustrates you are not telling the truth, you will be instantly declined.
It's OK that you have defaults, that you have borrowed money from pay day lenders, that you have missed a credit card payment, missed telco payments etc. Whether it was 3 months ago or 3 years ago, that's OK too. Just be honest and provide the reason as to why the particular default or missed payment happened.
The only places which will "guarantee you an approval" are companies who offer "Rent To Own" type programs, but these types of offerings need to be very carefully scrutinised before signing any piece of paper. They often lock you in to payments for a period of time with huge penalties. You often even have to pay further payments after the rent period to own the car outright.