GM bulletin 23-NA-021
What it saysThis service bulletin advises the tech that the rotational Clicking Noise Heard After Engine Shut Down may be normal characteristics of the vehicle. NHTSA’s full summary ↓
GM filed this with NHTSA as a service bulletin dated Oct 29, 2024, received Mar 1, 2023, about the power train — 3 documents under this number. It names 87 model years across Chevrolet, GMC, Buick and Cadillac (2017–2025). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
One page for every brand it was filed under. Each brand’s bulletins: Chevrolet · GMC · Buick · Cadillac.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThis service bulletin advises the tech that the rotational Clicking Noise Heard After Engine Shut Down may be normal characteristics of the vehicle.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 23-NA-021 | Service bulletin | Oct 29, 2024 | 11011225 | PDF, 124 KB |
| 23-NA-021 | Service bulletin | Nov 16, 2023 | 10245570 | PDF, 71 KB |
| 23-NA-021 | Service bulletin | Feb 15, 2023 | 10232157 | PDF, 499 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 themChevrolet 31 model years
GMC 11 model years
and 2 more on this site: 2019 GMC Terrain, 2018 GMC Terrain.
Buick 26 model years
and 18 more on this site: 2024 Buick Encore, 2023 Buick Encore, 2022 Buick Encore, 2021 Buick Encore, 2020 Buick Encore, 2025 Buick Envision, 2024 Buick Envision, 2023 Buick Envision, 2022 Buick Envision, 2021 Buick Envision, 2020 Buick Envision, 2019 Buick Envision, 2018 Buick Envision, 2019 Buick LaCrosse, 2018 Buick LaCrosse, 2020 Buick Regal, 2019 Buick Regal, 2018 Buick Regal.
Cadillac 19 model years
and 11 more on this site: 2024 Cadillac XT5, 2023 Cadillac XT5, 2022 Cadillac XT5, 2021 Cadillac XT5, 2020 Cadillac XT5, 2025 Cadillac XT6, 2024 Cadillac XT6, 2023 Cadillac XT6, 2022 Cadillac XT6, 2021 Cadillac XT6, 2020 Cadillac XT6.
A 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 87 model years this bulletin names have filed 8,474 complaints with NHTSA since 2015. 6,188 of them name Engine, Electrical System, Power Train — 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.
On the 2017 Chevrolet Malibu, the 147 owners who gave an odometer reading for Engine reported it at a median of 58,410 miles. That figure is one model year’s, not the whole range this bulletin covers — medians from different model years are not averaged.
Engine problem loss of power intermittently no reverse. They replaced clutch parts seals, piston, rings, plates, and plates. Had Vehicle for about 22 days. Driving home after repairs completed. Cluster display- instrument panel went out. Called Dealer and Cadillac assistance. Says there nothing they can do until Cadillac releases a fix.
2024 Cadillac XT5 · Engine · filed with NHTSA Jun 24, 2024 · ODI 11596124
On February 4, 2026, my wife drove to the bank, a trip of about 10 to 15 minutes, and turned off the car at the ATM. When she tried to leave, the vehicle wouldn't start. After a while, she opened and closed the door and locked and unlocked the car twice with the remote control, and the vehicle started and she was able to drive, but all…
2024 Chevrolet Blazer · Electrical System · filed with NHTSA Feb 5, 2026 · ODI 11715867
Second time in less than a month on a 2018 Buick Enclave that air conditioning unit/evaporator in vehicle is not working and vehicle is blowing hot air only. This occurs whether vehicle is in motion or stationary. This happens when vehicle is first powered on or over an extended drive (45 mins). Does not oscillate with change in speed.
2018 Buick Enclave · Power Train · filed with NHTSA Oct 14, 2020 · ODI 11364327
In depth: 2020 Chevrolet Blazer engine problems → · 2020 Chevrolet Blazer electrical problems → · 2020 Chevrolet Blazer transmission and drivetrain problems → · 2019 Chevrolet Blazer electrical problems →
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 power train
Source: same model, same component group103 other manufacturer communications filed against these GM models under the same component group (power train), newest first. The eight newest are listed; the rest are on the Chevrolet list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| N252502891-01 | Service campaign | Aug 20, 2026 | Certain vehicles may have a condition in which the internal differential nut was cross threaded or missing during assembly. Dealers will rev… |
| N252502890-01 | Service campaign | Aug 20, 2026 | Certain vehicles may have a condition in which the internal differential nut was cross threaded or missing during assembly. Dealers will rev… |
| N242471460-01 | Service campaign | Aug 20, 2026 | Certain vehicles may have been built with an Electric Drive Unit mounting bolt that is too long, causing damage to the Drive Unit case. Deal… |
| PIE0814B | Service bulletin | May 7, 2025 | This engineering information (EI) closure ends the need for requesting further information from technicians in regard to the Service AWD Lam… |
| PIP6036A | Service bulletin | Apr 2, 2025 | This Preliminary information communicates diagnostic aids for a surge or fishbite concern |
| 25-NA-001 | Service bulletin | Mar 13, 2025 | This service bulletin provides repair information to correct a customer concern of a transmission fluid leak. |
| PIE0814A | Service bulletin | Mar 12, 2025 | This engineering information (EI) is requesting information from technicians to perform the check list provided and contact the engineer lis… |
| 24-NA-232 | Service bulletin | Mar 7, 2025 | This technical bulletin provides repair information to correct a customer concern of Metallic Noise from Rear Differential on Acceleration. |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Chevrolet, GMC, Buick and Cadillac, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is GM 23-NA-021 a recall?
No. A service bulletin 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 23-NA-021 repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way. Every GM warranty extension on file lists the ones GM has filed.
Which vehicles does 23-NA-021 cover?
The manufacturer filed it against 87 model years across 4 brands (Chevrolet, GMC, Buick and Cadillac): 2024 Buick Enclave, 2023 Buick Enclave, 2022 Buick Enclave, 2021 Buick Enclave, 2020 Buick Enclave, 2019 Buick Enclave and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.