An exhaust advisory means the tester noted the exhaust without it reaching a defect level. An insecure exhaust is a major defect, one likely to fall off is dangerous, and a leak that could affect emissions is a major defect.
Checked 23 October 2026 against the DVSA MOT inspection manual
- Insecure exhaust: Major defect
- Likely to detach: Dangerous defect
- Leak affecting emissions: Major defect
- DVSA manual: 8.1 and 8.2
What this advisory means
An advisory is the written comment an MOT tester records when an exhaust item is not deteriorated enough to justify a fail, so the presenter is informed of its condition. An advisory does not cause a fail and is recorded in the MOT history. It documents what the tester observed at the time of the test, so the item can be monitored at future tests.
The advisory sits alongside the defects that do fail a test. An insecure part of the noise suppression system is a major defect under DVSA manual 8.1.1 b i, and a part likely to become detached is dangerous under 8.1.1 b ii. Exhaust noise above permitted levels is a major defect, and an exhaust or induction leak that could affect emissions is major under 8.2.1.1 b. Emission control equipment that is missing, obviously modified or defective is also major.
It stays on the MOT history and is visible to anyone checking the record. Where the same exhaust item later deteriorates to the point of insecurity, detachment risk, excess noise or an emissions affecting leak, it moves from advisory to major or dangerous defect and the vehicle fails.
When it becomes an MOT fail
An advisory only becomes a fail when the condition crosses a threshold set out in the DVSA inspection manual. For the exhaust system, an insecure part of the noise suppression system is recorded as a major defect under 8.1.1 b i. Where that part is likely to become detached, the defect is dangerous under 8.1.1 b ii. Exhaust noise above permitted levels is also a major defect. These are the specific conditions that turn a written comment into a failure at the test.
Separately, an exhaust or induction leak that could affect emissions is a major defect under 8.2.1.1 b. Emission control equipment that is missing, obviously modified or defective is major as well. The manual references matter because they show the exact point at which the tester must record a defect rather than an advisory. A comment about a part that remains secure and within noise limits stays an advisory; the same part, once insecure or likely to detach, moves to major or dangerous.
The fail arises only from the condition described in the manual, not from the presence of the advisory. Where the criteria in 8.1.1 or 8.2.1.1 are met, the defect is recorded as major or dangerous and the vehicle fails. Where they are not met, the advisory stands alone.
| DVSA manual ref | Defect | Result |
|---|---|---|
| 8.1.1 (a) | Exhaust noise above permitted levels | Major |
| 8.1.1 (b)(i) | Part of the exhaust system insecure | Major |
| 8.1.1 (b)(ii) | Part of the exhaust likely to become detached | Dangerous |
| 8.2.1.1 (b) | Exhaust leak that could affect emissions | Major |
Source: DVSA manual section 8: nuisance, checked 23 October 2026.
Frequently asked questions
What does an MOT advisory on the exhaust mean?
An advisory is used when an item is not deteriorated enough to justify a fail, to inform the presenter. Advisories do not cause a fail and are recorded in the MOT history.
Does an exhaust advisory mean the car has failed its MOT?
No. Advisories do not cause a fail. An advisory is used when an item is not deteriorated enough to justify a fail, to inform the presenter, and it is recorded in the MOT history.
When does an insecure exhaust become a fail?
An insecure part of the noise suppression (exhaust) system is a major defect under DVSA manual 8.1.1 b i. If it is likely to become detached, it is a dangerous defect under 8.1.1 b ii.
Is exhaust noise above permitted levels an MOT failure?
Yes. Exhaust noise above permitted levels is a major defect. An exhaust or induction leak that could affect emissions is also a major defect under 8.2.1.1 b.
What about missing or modified emission control equipment at MOT?
Emission control equipment that is missing, obviously modified or defective is a major defect. An exhaust or induction leak that could affect emissions is a major defect under 8.2.1.1 b.
