ISO 14229-1:2026: what the new UDS edition changes, and what it does not

In June 2026 ISO published the fourth edition of ISO 14229-1, the application layer of Unified Diagnostic Services. For most programmes the technical change is small. The work it creates is mostly in documents that cite the old edition by date.

What was published

ISO 14229-1:2026 was published on 5 June 2026. Its foreword states that it cancels and replaces the third edition, ISO 14229-1:2020, which has been technically revised, and that it incorporates the amendment ISO 14229-1:2020/Amd 1:2022. The 2020 edition and its amendment are now withdrawn.

The part numbering is unchanged. ISO 14229-1 is still the data-link-independent application layer, and the transport and session parts sit where they did. UDS over CAN still runs through ISO 15765, and UDS over IP still runs through DoIP (ISO 13400).

What changed

The foreword lists one main change: corrections related to the ResponseOnEvent service, SID 0x86. ResponseOnEvent lets a tester ask an ECU to send responses on its own when a defined event occurs, for example a change in a DTC status or in a data identifier, instead of polling for it. The corrections matter to the programmes that implement it.

The 2022 amendment, which until now had to be read alongside the 2020 text, is folded into the main document. For anyone working from the 2020 edition plus amendment, the consolidated text is simply easier to cite.

What did not change

The service set is the one engineers already know. The table of contents of the 2026 edition carries the same functional units: diagnostic and communication management, data transmission, stored data, input/output control, routines and upload/download. SecurityAccess (0x27) is still there. So is Authentication (0x29), with both of its modes: Authentication with PKI Certificate Exchange and Authentication with Challenge-Response. The non-volatile memory programming process, with its pre-programming, programming and post-programming steps, is still part of the standard.

In other words, nothing in the 2026 edition asks you to redesign a flash sequence or a security concept. The services described in our guide to UDS apply as written.

What to update

Specifications and requirements. Diagnostic specifications, supplier requirements and statements of work often cite “ISO 14229-1:2020”. Decide whether new documents should cite the 2026 edition or the standard without a year, and do it deliberately. A dated reference pins a contract to a withdrawn text. An undated one moves with the standard, which is not always what a supplier agreement intends.

ResponseOnEvent. If your ECUs or testers implement 0x86, review the implementation and its test cases against the corrected text. If they do not, note that in the specification, so the question does not come back at every review.

Test suites. Conformance and regression suites that reference clause numbers or the 2020 text should be checked against the new edition. This is a small task if the suite is automated and maintained, and a large one if it lives in spreadsheets.

The record. Note which edition each ECU, tool and test suite was built and verified against. A platform will carry both editions for years. Knowing exactly what runs on each vehicle is the same discipline UN R156 and ISO 24089 ask for, applied to the standards themselves.

Where this leaves you

A new edition of a standard this central is worth reading, but not worth a project. The protocol has not moved. What has moved is the reference, and the programmes that keep their references, test cases and records in order will absorb it quickly.