Hvad fejler bilen?

Because Danish main-clause questions use verb-second / inversion word order.

• Hvad fejler bilen? = What is wrong with the car?
• Literally, it is closer to What ails the car?

In a Danish question, the finite verb usually comes before the subject:

• Hvad fejler bilen?
  • hvad = what
  • fejler = is wrong with / ails
  • bilen = the car

But hvad bilen fejler can appear inside a subordinate clause, for example:

• Jeg ved ikke, hvad bilen fejler.
• I don’t know what is wrong with the car.

So:

• Hvad fejler bilen? = correct as a direct question
• hvad bilen fejler = correct inside a longer sentence

Here fejler means is wrong with or ails.

It is the present tense of fejle. In this kind of sentence, it is used to ask what problem something has.

So:

• Hvad fejler bilen? = What is wrong with the car?

This use is common with both people and things:

• Hvad fejler du? = What’s wrong with you?
• Hvad fejler computeren? = What’s wrong with the computer?

A learner may know fejl as mistake/error. That is related, but in this sentence fejler does not mean makes a mistake. It means has something wrong with it.

Because Danish does not use do-support the way English does.

In English, we often need do/does/did to form questions:

• What does the car have wrong?
• What does he want?

Danish normally just changes the word order:

• Bilen fejler noget. (not a natural everyday sentence, but it shows the structure)
• Hvad fejler bilen?

So Danish forms the question by moving the verb into question position, not by adding a helper verb like does.

Because Danish usually puts the definite article at the end of the noun.

• bil = car
• bilen = the car

This is very common in Danish:

• bog = book
• bogen = the book
• mand = man
• manden = the man

So bilen is one word meaning the car.

The noun bil is a common-gender noun, so its indefinite and definite forms are:

• en bil = a car
• bilen = the car

Fejler is the present tense form of fejle.

Danish verbs do not change for person the way English verbs do. The same form is used with different subjects:

• jeg fejler
• du fejler
• han fejler
• bilen fejler

That means fejler is simply the present-tense form, regardless of whether the subject is I, you, he, or the car.

Yes, it is natural and correct.

But many speakers might also very commonly say:

• Hvad er der galt med bilen?
• What is wrong with the car?

Both are good Danish. A rough difference is:

• Hvad fejler bilen? = a bit more direct, using the verb fejle
• Hvad er der galt med bilen? = very common everyday way to ask the same thing

So if you learn either one, you are learning useful Danish.

Yes, it can definitely be used for people too.

Examples:

• Hvad fejler du? = What’s wrong with you?
• Hun fejler ikke noget. = There’s nothing wrong with her.
• Hvad fejler barnet? = What’s wrong with the child?

So fejle can refer to:

• illness
• pain
• emotional trouble
• malfunction or damage in things

That is why it works with bilen as well as with people.

No, that is not correct.

With fejle in this structure, you do not use med.

Correct:

• Hvad fejler bilen?

If you want to use med, you would normally use the other common expression:

• Hvad er der galt med bilen?

So:

• Hvad fejler bilen? ✅
• Hvad er der galt med bilen? ✅
• Hvad fejler med bilen? ❌

A rough English-friendly guide would be:

• Hvad ≈ va(d)
• fejler ≈ FYE-luh
• bilen ≈ BEE-lən

So the whole sentence is roughly:

• va FYE-luh BEE-lən?

A couple of important notes:

• hvad is often pronounced much shorter and softer than it looks
• ej in fejler sounds like the eye sound in English
• the final -er is usually a weak vowel sound, not a strong English r

So the spelling looks harder than the actual spoken sentence.