need表示“需要”时,后接动词的ing形式,用主动形式表示被动意义,相当天to be done.本句可翻译为“汽车需要修理”,从语态的角度理解应当是“汽车需要被修理.”也可以用不定式表示为：It needs to be mended.
类似的还有require,want等.例如：
The problem requires discussing.= The problem requires to be discussed.
The screen wants cleaning.= The screen wants to be cleaned.那need to do sth 呢？