sidong beoteungwa josuseok muneul hwaginhaessseupnida.

I checked the ignition button and the front passenger door.

Breakdown of sidong beoteungwa josuseok muneul hwaginhaessseupnida.

• 문: the door
• 확인하다: to check
• 버튼: button
• 조수석: the front passenger seat

Questions & Answers about sidong beoteungwa josuseok muneul hwaginhaessseupnida.

What does 과 mean in this sentence?

과 means and and connects the two nouns:

• 시동 버튼과 조수석 문을
• the start button and the passenger-side door

A useful point: 과 is a slightly more formal/literary version of 와.
In everyday speech, people often use:

• 와 / 과
• 하고
• (이)랑

So this sentence sounds natural and a bit formal, which matches the ending -습니다.

Why is 을 attached only once at the end, instead of attaching it to both nouns?

Because the two nouns are being treated as one combined object:

• 시동 버튼과 조수석 문 = the start button and the passenger-side door
• then 을 marks that whole phrase as the object

So:

• 시동 버튼과 조수석 문을 확인했습니다
  means checked the start button and the passenger-side door

Korean often puts the case particle only on the last noun in a coordinated phrase like this.

You could also sometimes see both nouns marked in other contexts, but here marking only the final noun is very normal and natural.

What exactly is 확인했습니다 grammatically?