Short answer. Yes. Someone who has a right in or to the pledged thing may pay off the debt once it falls due, and the creditor cannot refuse in order to press on with a sale. Even a person with no interest in the item can usually pay under the general rules on payment.
What the law says
Any third person who has any right in or to the thing pledged may satisfy the principal obligation as soon as the latter becomes due and demandable.
Civil Code, Article 2117 — Third Person's Right to Satisfy the Debt. Read the full provision →
Who the article is written for
It speaks of a third person who has any right in or to the thing pledged. That is a wider group than it first sounds: a co-owner of the item, an heir with a share in it, someone holding a later claim over the same property, a buyer who acquired it subject to the pledge. Their common problem is that a sale would wipe out an interest of their own, and they have no way to protect it if only the debtor is allowed to pay. The article removes that helplessness. Their right to pay does not depend on the debtor's cooperation or on the creditor's willingness to deal with them.
Timing, and what the creditor must accept
The right arises as soon as the principal obligation becomes due and demandable, which is also the moment the creditor's power to foreclose comes alive. That pairing is deliberate. Once the debt is payable, the creditor's legitimate interest is in receiving the money, not in keeping the item, so he cannot brush aside a valid tender in order to reach the auction. What the article does not do is let anyone pay early to head off a sale that is not yet possible, or force the creditor to accept part of the amount. A tender that is short of what is due is not satisfaction of the obligation.
A friend or relative with no stake in the item
Most people asking this question are not co-owners of anything. They are a sibling or a parent trying to stop a family item going to auction. They are not covered by this article, but they are not shut out either: under the general rules on payment, a debt may be paid by a third person, and a creditor who is being handed the full amount ordinarily has no basis to refuse it. The practical difference lies in what happens afterwards, which turns on whether the debtor knew of and agreed to the payment. That question decides how much the payer can recover and what rights he takes over.
Paying is not the same as forgiving
Whoever pays, the debt does not vanish — it moves. The person who settled it can recover from you, and depending on the arrangement he may step into the creditor's shoes, security and all. Families routinely skip this conversation and regret it. Say plainly, before the money changes hands, whether it is a gift, a loan or a payment the payer expects to be reimbursed for, and put that in writing. Then make sure the payment is properly receipted, that the creditor acknowledges the obligation as settled, and that the item is actually released and returned rather than quietly kept on some other account.