GMC bulletin 661.20
GMC filed this with NHTSA as a over-the-air update dated Jun 10, 2026, received Apr 1, 2026, about the unknown or other — 8 documents under this number. It names 10 model years (2024–2026). 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 communication• This update contains a required software change to help improve the overall software update and diagnostics process. Be sure to install this update to be able to receive future software updates. • Improves traction and stability control when accelerating or on uneven terrain. • Improves braking and stopping performance on low-traction surfaces. • Improves the performance of assisted braking features.
Documents filed under this number
| Document | Kind | Dated | NHTSA id |
|---|---|---|---|
| 661.20 | Over-the-air update | Jun 10, 2026 | 11034055 |
| 661.20 | Over-the-air update | May 1, 2026 | 11031828 |
| 661.20 | Over-the-air update | Apr 14, 2026 | 11031789 |
| 661.20 | Over-the-air update | Apr 14, 2026 | 11031788 |
| 661.20 | Over-the-air update | Apr 2, 2026 | 11030537 |
| 661.20 | Over-the-air update | Mar 27, 2026 | 11030524 |
| 661.20 | Over-the-air update | Mar 21, 2026 | 11030538 |
| 661.20 | Over-the-air update | Feb 23, 2026 | 11030459 |
The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5; the full text comes from the manufacturer or a dealer. 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. Quote it at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themAlso filed against model years this site has no page for: 2026 GMC Hummer EV Pickup; 2026 GMC Hummer EV SUV.
A 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 GMC 661.20 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 661.20 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 661.20 cover?
The manufacturer filed it against 10 model years: 2026 GMC Sierra, 2025 GMC Sierra, 2024 GMC Sierra, 2025 GMC Sierra 2500HD, 2026 GMC Terrain, 2025 GMC Terrain and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.