What does 4.5.1 mean on an MOT certificate?

It refers to sub-section 4.5.1 of the MOT inspection manual, "Presence, condition and operation", within section 4, lamps, reflectors and electrical equipment. The letter or letters after it — (a), (b)(i) and so on — identify the specific defect from the 6 listed here. 3 Major and 3 Minor.

Which presence, condition and operation defect is recorded most often?

"An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning" (4.5.1 (a)(ii)), recorded about 1.1 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.

Section 4 · Lamps, reflectors and electrical equipment

4.5.1 Presence, condition and operation

Manual indexed 3 September 2026

Quick answer

Sub-section 4.5.1 of the MOT inspection manual covers presence, condition and operation and lists 6 defects. A reference like "(4.5.1 (a)(i))" on a certificate points to the matching row below. The most recorded is "An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning", about 1.1 times per 100 failed tests.

Official wording

The defect clauses

4.5.1 (a)(i)Minor
A front or rear fog lamp with a multiple light source up to 1/2 not functioning
4.5.1 (a)(ii)Major1.1 per 100 fails
An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning
Lamp not working explained: what it means and what puts it right
4.5.1 (b)(i)Minor
A lens defective which has no effect on emitted light
4.5.1 (b)(ii)Majorunder 0.1 per 100 fails
A lens defective such that emitted light is adversely affected
4.5.1 (c)(i)Minor
A front or rear fog lamp not securely attached
4.5.1 (c)(ii)Majorunder 0.1 per 100 fails
A front or rear fog lamp likely to become detached

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. 1 of 6 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 4

Other sub-sections of lamps, reflectors and electrical equipment

All sections of the manual

Common questions

What does 4.5.1 mean on an MOT certificate?: It refers to sub-section 4.5.1 of the MOT inspection manual, "Presence, condition and operation", within section 4, lamps, reflectors and electrical equipment. The letter or letters after it — (a), (b)(i) and so on — identify the specific defect from the 6 listed here. 3 Major and 3 Minor.
Which presence, condition and operation defect is recorded most often?: "An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning" (4.5.1 (a)(ii)), recorded about 1.1 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.