Kia over-the-air update SA621
What it saysThis 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. NHTSA’s full summary ↓
Kia filed this with NHTSA as an 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). An 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.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationWhat it applies to, as the document itself states it — the build window in the manufacturer’s own words, read by machine from the PDF NHTSA serves. The build date is on the certification label in the driver’s door jamb; the dealer settles a borderline vehicle by its VIN.
TECHNICAL 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 | PDF, 141 KB |
| TSB_ENG258 | Service bulletin | Sep 13, 2025 | 11023283 | PDF, 469 KB |
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.
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What owners reported
Source: NHTSA complaint databaseOwners of the 1 model year this bulletin names have filed 47 complaints with NHTSA since 2015. 24 of them name Electrical System, Engine — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.
The digital instrument panel (including infotainment screen) has occasionally turned off and back on. An article showed Kia and Hyundai were going to have a recall at the end of March for this problem, but noted only 2025 K4 vehicles built after Aug 4, 2025 were involved, while the door frame shows my vehicle built 7/2025.
2025 Kia K4 · Electrical System · filed with NHTSA Feb 3, 2026 · ODI 11715310
A complaint is one owner’s account, not a defect finding, and a bulletin is not a recall. Nothing here says this bulletin was issued because of these complaints, or that the repair it describes fixed them. Complaint files on this site begin in 2015.
More bulletins about the engine
Source: same model, same component group1 other manufacturer communication filed against the Kia K4 under the same component group (engine), newest first.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| DC26 | Service campaign | Feb 10, 2026 | TECHNICAL SERVICE BULLETIN: DATA COLLECTION: EXTRACT CALIFORNIA EMISSIONS DATA FROM ECU (DC26) - This bulletin has been revised to include a… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Kia, by the number printed on the letter.
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. The document itself sets the build window: built 3 Jul 2024 – 28 Apr 2025 — the build date is on the certification label in the driver’s door jamb.