هذا فحص المركبة.

In Arabic, the verb to be is usually omitted in simple present-tense statements.

So:

• هذا = this
• فحص المركبة = the vehicle inspection

Together, هذا فحص المركبة means This is the vehicle inspection.

If you wanted a past or future meaning, Arabic would use a verb, but in the present it is normally left out.

هذا means this.

More specifically, it is the masculine singular demonstrative used for something near the speaker.

In this sentence, it points to فحص المركبة as a whole: this vehicle inspection / this is the vehicle inspection.

Because the main noun in the expression is فحص (inspection), and فحص is masculine.

Even though المركبة (vehicle) is feminine, the demonstrative matches the head noun فحص, not the second noun in the phrase.

So:

• هذا فحص... = correct
• هذه فحص... = not correct

If the main noun were feminine, then you would use هذه.

It is an iḍāfa construction, often called a construct phrase.

This is a very common Arabic structure meaning X of Y.

So here:

• فحص = inspection
• المركبة = the vehicle

Together:

• فحص المركبة = inspection of the vehicle
  or more naturally, the vehicle inspection

In an iḍāfa, the first noun is the main noun, and the second noun tells you what it is connected to.

In an iḍāfa construction, the first noun normally does not take الـ.

So Arabic says:

• فحص المركبة

not:

• الفحص المركبة

That would be incorrect.

Even without الـ on فحص, the whole phrase can still be definite because the second noun is definite.

Because in an iḍāfa, definiteness is determined by the second noun.

Since المركبة has الـ and means the vehicle, the whole phrase becomes definite:

• فحص مركبة = an inspection of a vehicle / vehicle inspection
• فحص المركبة = the inspection of the vehicle / the vehicle inspection

So even though فحص looks indefinite by itself, the whole expression is definite.

Literally, it is:

• هذا = this
• فحص = inspection
• المركبة = the vehicle

So the literal structure is:

• This [is] inspection-of-the-vehicle

More natural English is:

• This is the vehicle inspection
• or This is the inspection of the vehicle

In fully vocalized, formal MSA, it would be:

• هٰذا فَحْصُ الْمَرْكَبَةِ

A careful pronunciation would be roughly:

• hādhā faḥṣu l-markabati

Why those endings?

• فحصُ is the predicate of the sentence, so it is nominative.
• المركبةِ is the second term of the iḍāfa, so it is genitive.

In normal writing and everyday reading, these short vowel endings are usually not written or fully pronounced.

The final ة is called tāʾ marbūṭa.

In pause, at the end of the sentence, it is usually pronounced like -a or -ah:

• al-markaba / al-markabah

In fully inflected formal reading, because the word is genitive here, you may hear:

• al-markabati

So learners often see ة and wonder whether it is t or h. The short answer is:

• in pause: usually -a / -ah
• with full grammatical ending: often -t before the case vowel

Not exactly.

مركبة is more general than car. It means vehicle and can refer to different kinds of vehicles depending on context.

If you specifically mean car, Arabic often uses:

• سيارة

So:

• فحص المركبة = vehicle inspection
• فحص السيارة = car inspection

For this exact meaning, هذا فحص المركبة is the natural order.

It works as:

• هذا = topic / demonstrative
• فحص المركبة = what it is

If you move the words around, you may get an unnatural sentence or change the meaning.

So for a learner, it is best to keep this pattern:

• هذا + noun phrase

Examples:

• هذا كتاب الطالب = This is the student’s book
• هذا باب البيت = This is the door of the house

Your sentence follows the same pattern.