Having an existing personal loan doesn't automatically preclude you from getting a car loan, but it does reduce your available options because the bank calculates your total monthly payments and obligations relative to your income and reviews your credit report.
Key points
Before applying, add up your personal loan, credit card balance, and any other BNPL or financing.
If the interest rate is high, increasing your down payment or choosing a cheaper car might be a smarter approach than significantly extending the loan term.
The figures, fees and limits in this answer vary by bank and change over time — confirm them with your bank or the official source before acting.