WORD OF CAUTION.

Depends on the legal implication of the seller.

Warranty is a specific time in which an item is covered.

A Guarantee is nothing really but an exclaimation of validity.

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Guarantee:

1. Something that assures a particular outcome or condition: Lack of interest is a guarantee of failure.
A. A promise or an assurance, especially one given in writing, that attests to the quality or durability of a product or service.
B. A pledge that something will be performed in a specified manner.

1. A guaranty by which one person assumes responsibility for paying another's debts or fulfilling another's responsibilities.
2. A guaranty for the execution, completion, or existence of something.
4. A guarantor.


Warranty

1. Official authorization, sanction, or warrant.
2. Justification or valid grounds for an act or a course of action.
3. Law.
1. An assurance by the seller of property that the goods or property are as represented or will be as promised.
2. The insured's guarantee that the facts are as stated in reference to an insurance risk or that specified conditions will be fulfilled to keep the contract effective.
3. A covenant by which the seller of land binds himself or herself and his or her heirs to defend the security of the estate conveyed.
4. A judicial writ; a warrant.
4. A guarantee given to the purchaser by a company stating that a product is reliable and free from known defects and that the seller will, without charge, repair or replace defective parts within a given time limit and under certain conditions.

Lo estoy dando como respuesta por separado, porque la fundamentación que da Fernando no es la adecuada. En este sentido de tu contexto, "warrants" como verbo significa "asegura, garantiza, da como cierto que".

warrant
transitive verb (past war·rant·ed, past participle war·rant·ed, present participle war·rant·ing, 3rd person present singular war·rants)
1. serve as a reason: to serve as a justifiable reason to do, believe, or think something
2. guarantee: to guarantee something such as the truth or dependability of something or somebody
3. authorize: to give authority to somebody
4. law guarantee title: to guarantee the title to property
5. state confidently: to state something with the confidence that it is true or will happen (archaic)


[12th century. From Old Northern French warant , variant of Old French guarant (source of English guarantee), from, ultimately, a prehistoric Germanic word meaning “to be on guard” (see ward).]


-war·rant·er, noun
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