Noun
Verb (する, intransitive)
1. fault; trouble; breakdown; failure; being out of order
故障かもしれないな。It might be a breakdown.
Noun
Verb (する, transitive)
2. damage (to a part of the body); injury; hurt
彼は、肩を故障した。He injured his shoulder.
3. problem; hitch; obstacle; hindrance
4. objection; protest