It's not illegal. If the car loan is overdue, some will remotely control the vehicle through GPS to realize power and oil cut-off. This kind of GPS is realized by jamming the key signal with electromagnetic signals. If you lock the car like this, the owner can't unlock it himself, so he can't start the car. We can only negotiate with the loan company to settle the arrears as soon as possible, and ask the people of the loan company to unlock it.

Legal basis:

People's Republic of China (PRC) Civil Code

Article 577 Where a party fails to perform its contractual obligations or fails to perform its contractual obligations in conformity with the contract, it shall be liable for breach of contract such as continuing to perform, taking remedial measures or compensating for losses.

Article 578 Where a party expressly expresses or shows by his own behavior that he will not perform his contractual obligations, the other party may require him to bear the liability for breach of contract before the time limit for performance expires.

Article 579 If one party fails to pay the price, remuneration, rent or interest, or fails to perform other monetary obligations, the other party may demand payment.