Serviceheftet viser når registerreimen ble skiftet.

Because Norwegian usually writes compound nouns as a single word.

So:

• servicehefte = service
  • hefte
• registerreim = register
  • reim

This is very common in Norwegian, much more so than in English. Where English often writes service booklet as two words, Norwegian normally combines them into one noun.

Serviceheftet means the service booklet or the maintenance booklet/record.

In this context, it is the booklet or record that shows the car’s maintenance history. So it is not just any booklet; it is specifically the one connected to service and repairs.

The ending -et makes the noun definite: the service booklet.

The base noun is et hefte = a booklet / a booklet-like pamphlet.
So:

• et servicehefte = a service booklet
• serviceheftet = the service booklet

In Norwegian, the definite article is often attached to the end of the noun instead of being a separate word like the in English.

Viser is the present tense of å vise, which means to show.

So:

• å vise = to show
• viser = shows

In this sentence, Serviceheftet viser ... means The service booklet shows ...

Yes, når does mean when, and here it introduces an indirect question:

• Serviceheftet viser når registerreimen ble skiftet.
• The service booklet shows when the timing belt was changed.

This is similar to English: shows when ...

A learner may wonder about da, since da can also relate to when in past-time situations. But da is not used here, because this is an indirect question. After a verb like viser, forteller, vet, husker, etc., Norwegian uses the question word når.

Registerreimen means the timing belt.

It is the definite singular form of registerreim. In car-related language, this is an important part of the engine. In English, it may also be called a cambelt in some varieties of English.

The ending -en is the definite ending for this noun, so it means the timing belt.

So:

• en registerreim = a timing belt
• registerreimen = the timing belt

Again, Norwegian usually adds definiteness to the end of the noun instead of using a separate word like the.

Yes. Ble skiftet is a passive construction and means was changed or was replaced.

Here is the breakdown:

• ble = past tense of å bli
• skiftet = past participle of å skifte

Together:

• ble skiftet = was changed / was replaced

This is a very common way to form the passive in Norwegian, especially when talking about an event that happened in the past.

Yes, absolutely. In this sentence, replaced is often the most natural English choice.

With car parts, å skifte often means:

• to change
• to replace

So registerreimen ble skiftet can very naturally mean the timing belt was replaced.

This part is a subordinate clause, and Norwegian usually has normal subject-verb order in subordinate clauses.

So:

• når = when
• registerreimen = the timing belt
• ble skiftet = was changed

The subject registerreimen comes before the verb ble.

That is different from main-clause word order in Norwegian, where the finite verb often comes in second position. Here, because it is an embedded clause after viser, the word order is more straightforward.

Yes, it is completely natural, especially in a practical or technical context such as car maintenance.

It sounds like something you might read or say when talking about service records for a vehicle. A very close alternative could be:

• Serviceheftet viser når registerreima ble skiftet.

That version uses registerreima, which is also common in many varieties of Norwegian. Both are natural, but registerreimen is a standard Bokmål form.