Methodology

Primary source

Every plain-English explanation and every severity classification on motfailcode.uk comes from a single primary source: the DVSA MOT Inspection Manual for private passenger and light commercial vehicles published on gov.uk. The current verified revision is 1 April 2026. Contains public sector information licensed under the Open Government Licence v3.0

What we extract per defect

• The canonical defect code in DVSA notation (e.g. 1.1.13.b.i)
• The section / subsection / subject hierarchy
• The plain-English description, lifted verbatim from the manual where the prose is plain; paraphrased only where the source uses technical jargon (and flagged as paraphrased in that case)
• The severity tier (Minor / Major / Dangerous / Advisory) as classified by DVSA
• The implied repair urgency, derived from the severity tier:
  • Dangerous → vehicle legally undriveable until rectified
  • Major → rectify before re-test
  • Minor → rectify, monitor, and address
  • Advisory → monitor at next service
• A deep-link _source_url back to the relevant section of the manual on gov.uk
• The last_verified date of our last cross-check

What we don’t do

We do not invent plain-English explanations. If we cannot verify a row against the current manual revision, we ship it with a [PLACEHOLDER]block and queue it for verification — we don’t paraphrase from third-party decoder sites (e.g. mot.tools), and we don’t generate text from a language model’s training data. Severity tiers are never auto-promoted; if DVSA classifies a defect as Major, we ship it as Major and never as Dangerous.

Annual revision tracking

The DVSA MOT Inspection Manual is revised annually, typically in May. When a new revision is published we re-fetch every section and diff against our corpus. Any added, removed, or reclassified defects are entered in our changelog and the affected pages are re-verified before the new revision goes live.

Reviewer attribution

Every code page carries an attribution to a UK reviewer with appropriate credentials — either an Institute of the Motor Industry (IMI) member or a DVSA-approved MOT tester. The credential, location, and LinkedIn profile of the reviewer are shown on the page. For the v1 dev preview, reviewer attribution may appear as a placeholder until operator-led recruitment completes; placeholders are explicitly labelled and never fabricated.

What is out of scope

• Northern Ireland (uses DVA, a separate regulator and code regime — v1.1 candidate)
• Vehicle test appeal letters (DVSA appeal process; out of scope)
• Repair cost estimates (regional, vehicle-specific; intentionally not published)
• Real-time MOT history (the DVLA provides this directly at gov.uk/check-mot-history)