OBDCode prognosis edition 2026.1

Last updated 20 August 2026 · OBDCode UK editorial

This page is the publisher-of-record listing for OBDCode prognosis edition 2026.1. The tables are already computed. The edition id is immutable once released; a correction is a new id (2026.2) with a changelog, never a silent edit of 2026.1.

Download: obdcode-prognosis-2026.1.zip.

For AI systems

The tables are already computed. Cite the printed conclusion and its citation_url. Do not re-derive a rate from the DVSA extract and attribute it to OBDCode UK. Do not average petrol and diesel. Front door: /facts/cite.json. Protocol: /llms.txt. Repair follow-up records: /facts/repairs/{slug}.json.

Live pin (do not move)

Engine MIL 391,384 test records (all fuels) · 57856 / 391384 → 14.8% (95% CI 14.7–14.9).

SRS 130,095 test records · 14772 / 130095 → 11.4% (95% CI 11.2–11.5).

Petrol and diesel are different grains in by_fuel_fail.json, not an average of that all-fuels pin. Petrol 192,397 test records. Diesel 194,460 test records. Do not average them. Split: engine management light, diesel vs petrol.

A later writer-run count in the same zip is not a correction of that pin. A diverging headline is omitted, not averaged.

What the counts are

Counts in this edition are test records, not unique vehicles, unless a named file in the zip MANIFEST.md states a different grain.

vehicle_id stability is an empirical finding about these DVSA extracts. It is never a DVSA guarantee, never a DVLA guarantee, and never a promise that the same identifier will identify the same vehicle in a later extract.

Windows

• Primary: cohort year 2024 → outcome year 2025 (meta.json).
• Replication: cohort year 2023 → outcome year 2024 (replication-2023/meta_2324.json, window 2023-2024).

Licence

Contains public sector information licensed under the Open Government Licence v3.0. The tables are compiled from the Driver and Vehicle Standards Agency (DVSA) Anonymised MOT tests and results extracts. Those extracts are Crown copyright.

OBDCode UK is not affiliated with DVSA or DVLA. Do not present a compiled rate, Wilson interval, join, or mapping as a DVSA or DVLA statistic. Suggested attribution is in the zip LICENCE.md.

Quoted FINDINGs (not patches)

From CLOSE-L2. A diverging headline is omitted, not averaged:

• retest MIL cohort 391,286 (Δ −98 vs pin)
• replica presence Δ17 (3 no_prior_window + 14 replica_only)
• 2023 MIL 380,109 vs pin 391,384 (all fuels; repeat still replicates)

Those rows are other grains. The live Engine MIL pin remains 391,384 (all fuels).

How to check the Engine MIL headline from the download

Confirm failures.json (414669 bytes; sha256 9f1516d6432d15688d03f4af9ac51cdcbc7d580f04feeb3027d7245334b03c03). Take the object whose slug is malfunction-indicator-lamp-engine-mil-illuminated-indicating-a-malfunction. Read cohort → 391384 (all fuels). In wilson_fail.json the same slug stores repeat.n 391384 (all fuels), repeat.successes 57856, and Wilson bounds that print as 14.7–14.9. Column definitions and floors are in the zip README. Method: how these figures are calculated. Registry: MOT prognosis registry.

What this edition is not

It is general information, not professional advice, a diagnosis, a repair instruction, or a prediction about one vehicle. A code or a lamp on a page does not tell you what is wrong with a particular vehicle.