故障はエンジンにあるのかもしれない。

breakdown; failure; fault; accident; out of order; damage; hurt; objection; protest

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

engine

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to be (usu. of inanimate objects); to exist; to live; to have; to be located; to be equipped with; to happen; to come about

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

may; might; perhaps; may be; possibly

to become known; to come to light; to be discovered; to be known; to be understood; to obviously not amount to much; to seem trivial; to be evident; to be obvious; to go without saying; to be very intense (worry, hope, etc.); to be extremely severe