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Abgasuntersuchung (AU)

Technical testing centre (Technische Prüfstelle, e.g. TÜV or DEKRA) or supervisory organisation · Annex VIIIa

Part of the HUNo separate appointmentOn site

The most important piece of information on this subject is a negative one: the exhaust emission inspection (Abgasuntersuchung, AU) is not a separate appointment. Annex VIIIa StVZO describes the scope of the periodic roadworthiness test (Hauptuntersuchung, HU — commonly called ‘TÜV’) and explicitly lists exhaust gases under environmental impact. Anyone wanting to book an AU “in addition” is looking for a service that is already included in the appointment — and anyone looking for a separate AU sticker is looking for a document that no longer exists.

A sentence up front, because it sets the roles straight: TÜV and DEKRA are not authorities. Annex VIII StVZO transfers the Hauptuntersuchung to two private, state-recognised figures — the officially recognised experts or examiners for motor vehicle traffic (aaSoP) of the technical testing centres and the test engineers (PI) of the officially recognised supervisory organisations. They certify, they do not impose sanctions. Who may prohibit the operation of a vehicle is set out in § 29 StVZO and is a different body: “the authority competent under state law”. The Bußgeldstelle, in turn, imposes the regulatory fine. Three roles, three addressees.

Depending on the vehicle, testing follows two complementary methods. In modern vehicles, the engine management and emission control system is read out via the on-board electronics; alongside this is the measurement at the exhaust pipe. Annex VIIIa names as the inspection point the “exhaust behaviour — permissibility”; what matters are the limit values applicable to the specific vehicle, not a single uniform value for all.

In practice, this mainly has one consequence: a vehicle with an illuminated engine warning light or stored exhaust-relevant fault codes is highly likely to fail — and it fails as part of the Hauptuntersuchung, with all the consequences for the sticker. Having the fault codes read before the appointment is therefore the most effective preparation available here.

Last updated29 August 2026
Legal basisAnnex VIIIa StVZO
VerificationChecked against StVZO, Annex VIII and VIIIa, the catalogue of fines (Bußgeldkatalog) and the Driving Licence Ordinance (Fahrerlaubnis-Verordnung, FeV)
Written and reviewed byAndrés Sánchez Botta
Independent information website: we are not TÜV, DEKRA or any other testing organisation, not an authority and not a paid advice service – we do not submit applications on your behalf. All information comes from official sources and is explained here in plain language; binding information always comes from the competent body. No legal advice and not an official authority. We are neither lawyers nor tax consultants: we document official procedures and check the information against the official source – this is information, not legal or tax advice.
Separate appointmentNoPart of the HU
FrequencyWith the HUEvery 24 months for cars
Separate stickerNoOnly the HU sticker
PriceIncluded in the HU priceWorth asking about
Required documents

What you need

Registration certificate Part I (Zulassungsbescheinigung Teil I)

From it follow the engine type and emissions class — and hence the limit values against which the measurement is taken.

The most recent test report

It shows whether exhaust-relevant issues were already noted at the last appointment. These points are checked again.

Evidence of work on the exhaust system

Catalytic converter, particulate filter, lambda sensor, EGR valve (AGR): invoices and parts certificates help where components have been replaced — especially with non-original parts.

The read-out fault memory

Not a mandatory document, but the most effective preparation. Exhaust-relevant faults lead to failure, and they can be identified beforehand.

A vehicle at operating temperature

The measurement requires operating temperature. A short journey on a cold engine is an avoidable cause of abnormal readings.

Step by step

How to proceed

  1. 1

    Do not book separately

    The AU is part of the Hauptuntersuchung. A separate appointment is neither necessary nor provided for; if in doubt, ask what is included in the price quoted.

  2. 2

    Have the fault memory read before the appointment

    Exhaust-relevant entries practically always lead to failure. The read-out costs little and, in the best case, avoids the need for a re-test.

  3. 3

    Take the engine warning light seriously

    It is not an indicator of comfort-related issues, but as a rule exhaust-relevant. Driving to the HU with the light on is rarely a good idea.

  4. 4

    Arrive at operating temperature

    The readings are measured at operating temperature. Allow for a long enough drive beforehand so that the engine is not cold when you arrive.

  5. 5

    Check the result in the test report

    The exhaust readings are stated in the Hauptuntersuchung report. There is no separate certificate or sticker for the AU.

Fee information

Costs and payment

Classification and costsThe AU has no rate of its own
Legal basisAnnex VIIIa StVZO
Separate appointmentNot provided for
Separate stickerNot provided for
Test methodRead-out and exhaust pipe measurement
Limit valuesDepending on the vehicle
PriceIncluded in the HU price

Because the AU is part of the Hauptuntersuchung, there is no separate price for it. The sensible question is whether the quoted HU price includes it — with reputable providers, it does.

Good to know

Important notes

Anyone still looking for the AU sticker: it no longer exists. The result is stated in the test report of the Hauptuntersuchung, and only the HU sticker sits on the licence plate.

An illuminated engine warning light is the most likely reason for failing the exhaust part. Ignoring it before the appointment only postpones the problem — with the difference that a re-test is then added.

With modifications to the exhaust system, it is not only the measured value that counts, but also the permissibility of the component. Without evidence, the sticker can be withheld even if the readings are correct — in that case, § 19 StVZO applies, not the measurement.

No figure is given here as a nationwide amount for the prices. The Hauptuntersuchung is not an administrative fee and has no fee ordinance: it is calculated by the respective supervisory organisation or testing centre and varies between providers and regions. The binding information is that of the body where you book your appointment — and it is worth asking, because the range is real.

Avoid these mistakes

Common mistakes

Booking the AU as a separate appointment. Under Annex VIIIa, it is part of the Hauptuntersuchung.

Looking for an AU sticker. The result is stated in the test report.

Arriving with the engine warning light on. Exhaust-relevant faults lead to failure.

Arriving cold. The measurement is taken at operating temperature.

Fitting non-original exhaust parts without evidence. In that case, it is not the measurement that decides, but § 19 StVZO.

Frequently asked questions

Questions and answers

Do I need a separate appointment for the Abgasuntersuchung?

No. Annex VIIIa StVZO describes the scope of the Hauptuntersuchung and lists exhaust gases as an inspection point under environmental impact. The AU is therefore a component of the HU; a separate appointment is neither necessary nor provided for.

Is there still an AU sticker?

No. Only the inspection sticker of the Hauptuntersuchung sits on the licence plate. The result of the exhaust part is stated in the test report, not through a separate sticker.

How is it tested?

By two complementary methods: by reading out the engine management and emission control system via the on-board electronics, and by measurement at the exhaust pipe. Annex VIIIa names as the inspection point the exhaust behaviour and its permissibility; what matters are the limit values applicable to the specific vehicle.

What is the most common reason for failure?

Stored exhaust-relevant faults, usually indicated by the illuminated engine warning light. Reading the fault memory before the appointment is therefore the most effective preparation — it costs little and, in the best case, saves a re-test.

How much extra does the AU cost?

Nothing, because it is not a separate process. The sensible question is whether the quoted price for the Hauptuntersuchung includes it. There is no official rate either for the HU or for its components.

What applies to a modified exhaust system?

In that case, alongside the measured value, the permissibility of the component also counts. If a parts certificate, ABE or a modification approval (Änderungsabnahme) under § 19 Abs. 3 StVZO is missing, the sticker can be withheld even with faultless readings — it is then not the measurement that decides, but the operating licence.

Related official procedures

Periodic roadworthiness test (Hauptuntersuchung)
First after 36 months, then every 24
No official tariff
Re-test
One month — then a new HU
Nr. 3.1.4.3 Annex VIII
Modification approval (Änderungsabnahme)
Otherwise the operating licence lapses
§ 19 Abs. 3 StVZO

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