The MOT Files

Section 8 · Nuisance

8.2.1.2 Gaseous emissions

Manual indexed

Quick answer

Sub-section 8.2.1.2 of the MOT inspection manual covers gaseous emissions and lists 8 defects. A reference like "(8.2.1.2 (a))" on a certificate points to the matching row below. The most recorded is "Lambda coefficient outside the default limits or the range specified by the manufacturer", about 2.1 times per 100 failed tests.

Official wording

The defect clauses

  1. 8.2.1.2 (a)Major0.5 per 100 fails

    Emissions levels exceed the manufacturer’s specified limits

    Emissions above the permitted limit explained: what it means and what puts it right

  2. 8.2.1.2 (b)Major0.3 per 100 fails

    Emissions levels exceed default limits

    Emissions above the permitted limit explained: what it means and what puts it right

  3. 8.2.1.2 (c)Major2.1 per 100 fails

    Lambda coefficient outside the default limits or the range specified by the manufacturer

    Emissions above the permitted limit explained: what it means and what puts it right

  4. 8.2.1.2 (d)Major1.0 per 100 fails

    Emissions test unable to be completed

  5. 8.2.1.2 (e)Major

    Engine is idling clearly above its normal idle speed

  6. 8.2.1.2 (f)Major

    Exhaust emits dense blue or clearly visible black smoke for a continuous period of 5 seconds at idle

    Diesel emitting visible smoke explained: what it means and what puts it right

  7. 8.2.1.2 (g)Major

    Exhaust emits excessive dense blue or clearly visible black smoke during acceleration which would obscure the view of other road users

    Diesel emitting visible smoke explained: what it means and what puts it right

  8. 8.2.1.2 (h)Major

    Engine MIL inoperative or indicating a malfunction

    Engine management light on, or not working explained: what it means and what puts it right

Wording and categories reproduced from the DVSA inspection manual under the Open Government Licence. Frequencies are items per 100 failed class 4 tests across the DVSA anonymised MOT dataset; a clause with no figure was not recorded often enough to appear in any model’s top forty failure items. 6 of 8 clauses link to our own explanation.

Grading

What the categories mean

Dangerous
a direct and immediate risk to road safety or the environment. The vehicle fails and must not be driven until repaired, even to a garage.
Major
a defect that affects safety, the environment or other road users. The vehicle fails.
Minor
a defect with no significant effect on safety or the environment. Recorded on the certificate; the vehicle passes.

The full guide to defect grading

Section 8

Other sub-sections of nuisance

All sections of the manual

Common questions

What does 8.2.1.2 mean on an MOT certificate?
It refers to sub-section 8.2.1.2 of the MOT inspection manual, "Gaseous emissions", within section 8, nuisance. The letter or letters after it — (a), (b)(i) and so on — identify the specific defect from the 8 listed here. 8 Major and 0 Minor.
Which gaseous emissions defect is recorded most often?
"Lambda coefficient outside the default limits or the range specified by the manufacturer" (8.2.1.2 (c)), recorded about 2.1 times per 100 failed MOT tests nationally. We explain what it means and what puts it right.
Does a Minor defect fail the MOT?
No. a defect with no significant effect on safety or the environment. Recorded on the certificate; the vehicle passes. Major and Dangerous defects fail. A Dangerous defect also means the car must not be driven until it is repaired.