Kia bulletin SA621
Kia filed this with NHTSA as a over-the-air update dated Dec 2, 2025, received Sep 23, 2025, about the engine — 2 documents under this number: OTA_SA621, TSB_ENG258. It names 1 model year (2025). A over-the-air update is not a safety recall — there is no NHTSA campaign number and no federal requirement — but it is usually work the manufacturer pays for on the vehicles it names; the dealer checks the VIN against the manufacturer’s list.
What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationTECHNICAL SERVICE BULLETIN: SERVICE ACTION: ECM JUDGEMENT LOGIC IMPROVEMENT FOR DTC P218100 (SA621) - This bulletin provides information to upgrade the Engine Control Module (ECM) system software on certain 2025MY K4 (CL4m) vehicles produced from July 03, 2024 through April 28, 2025 equipped with an Nu 2.0L MPI engine. The vehicles affected may exhibit a MIL ‘ON’ with DTC P218100 stored under certain driving conditions such as high-load, high-speed driving in low temperature environments. There are no drivability or other symptoms associated with this condition. High-load control logic helps to lower the coolant temperature by allowing the valve of the Integrated Thermal Module (ITM) to fully open the radiator port during rapid acceleration.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| OTA_SA621 | Over-the-air update | Dec 2, 2025 | 11026532 | not yet checked |
| TSB_ENG258 | Service bulletin | Sep 13, 2025 | 11023283 | not yet checked |
The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themA vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
Common questions
Source: NHTSA, 49 CFR 579.5Is Kia SA621 a recall?
No. A over-the-air update is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the SA621 repair free?
A over-the-air update is usually paid by the manufacturer on the vehicles it names, within the terms and time limit the document sets; the dealer checks the VIN against the manufacturer’s list.
Which vehicles does SA621 cover?
The manufacturer filed it against 1 model year: 2025 Kia K4. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.