GM bulletin 21-NA-214
What it saysThis technical bulletin provides repair information to correct a customer concern of Service Engine Soon Lamp being illuminated. NHTSA’s full summary ↓
GM filed this with NHTSA as a service bulletin dated Aug 10, 2023, received Apr 6, 2022, about the power train — 2 documents under this number. It names 4 model years across Chevrolet and GMC (2020). 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.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThis technical bulletin provides repair information to correct a customer concern of Service Engine Soon Lamp being illuminated. They may also comment on multiple transmission issues including harsh or delayed shifts, slip, surge, shudder, noise, whine, growl, shake and/or vibration. As well as the exhaust brake not working or that they do not feel it. Technicians may find DTCs P2002, P2463, P2459, P144E, P0421, P0422, P0106 P20EE, P129F, P16F3, P20FF, P226D, P249D, P249E, P11CC and / or P11D5.
Trouble codes it names: P0106 P0421 P0422 P11CC P11D5 P129F P144E P16F3 P2002 P20EE P20FF P226D P2459 P2463 P249D P249E U0101 1 of 17 read from the document itself
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 21-NA-214 | Service bulletin | Aug 10, 2023 | 10242114 | PDF, 134 KB |
| 21-NA-214 | Service bulletin | Apr 1, 2022 | 10210030 | PDF, 127 KB |
What the document itself lists
The manufacturer titles it “Service Engine Soon Lamp Illuminated, Harsh or Delayed Transmission Shifts”.
Labour operation and the time the manufacturer allows
| Operation | Description | Time |
|---|---|---|
| 2888228 | ECM and TCM Reprogramming | 0.6 hrs |
Read by machine from the document NHTSA serves (7 pages), read Sep 30, 2026. A part number is shown only where it matches GM’s own catalogue shape, an operation only with its code and time, and a description only where the reader got it whole; anything it could not settle is left out, and the PDF is the record. Times are the manufacturer’s warranty allowances, not a quote. Listings and prices on eBay Motors are the seller’s.
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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 2 model years
GMC 2 model years
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 4 model years this bulletin names have filed 279 complaints with NHTSA since 2015. 226 of them name Power Train, Service Brakes, Electrical System — 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.
My vehicle inadvertently locks the rear tires at highway speeds and then releases and drives. In some instances it may brake several times causing the tires to burn rubber for a short distance causing rear traffic to either swerve to avoid rear ending me and in a couple instances causes the rear following traffic to abruptly change lanes…
2020 GMC Sierra 2500HD · Service Brakes · filed with NHTSA Mar 29, 2024
There is an issue that is causing the batteries to die. This in return causes the Vehicle to go into Limp home mode with no warning. The "issue" was supposed to be resolved by the Dealer in March 2022. The resolution was that one battery was bad. The vehicle is equipped with two batteries. Each of which is sufficient to run the vehicle.
2020 GMC Sierra 2500HD · Power Train · filed with NHTSA Jan 3, 2023
The contact owns a 2020 Chevrolet Silverado 3500. The contact stated that while driving on at 70-73 MPH, the vehicle unexpectedly downshifted to first gear. The contact slammed on the brake pedal and pulled over to the side of the road. The vehicle was turned off. The contact stated that the tachometer had increased to over 3,000 RPM.
2020 Chevrolet Silverado 3500HD · Engine · filed with NHTSA Feb 10, 2025
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 group58 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 |
|---|---|---|---|
| N262567720 | Service campaign | Sep 17, 2026 | Certain vehicles may have received transmission mounting bolts that do not meet expected hardness specifications. Loose or failed bolts may… |
| N262560680 | Service campaign | Jun 10, 2026 | Certain vehicles may have a condition in which the bolts for the transmission control valve body may be loose or missing. Dealers will retor… |
| N242454441 -03 | Service campaign | Oct 9, 2025 | Certain vehicles listed above, may have a condition where the transmission control valve has worn, resulting in a gradual loss of pressure w… |
| 24-NA-262 | Service bulletin | Jun 3, 2025 | This bulletin helps aid the tech in possible 10L100 transmission noise that may be normal or abnormal depending on the concern noted. |
| 22-NA-182 | Service bulletin | May 16, 2025 | This service bulletin advises the technician to check if the transmission cooler lines are twisted to correct customer concerns of Harsh Shi… |
| PIE0824A | Service bulletin | May 10, 2025 | This engineering information (EI) closure ends the need for gathering further information from field in regard to fluid leaking at the outpu… |
| 24-NA-075 | Service bulletin | May 8, 2025 | This bulletin provides a procedure to add a shim to the rear axle to change the pitch of said axle to correct the angle of the axle to pinio… |
| 21-NA-238 | Service bulletin | May 8, 2025 | This technical bulletin provides a procedure to inspect the front pump of the transmission for a possible leak. |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Chevrolet and GMC, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is GM 21-NA-214 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 21-NA-214 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.
Which vehicles does 21-NA-214 cover?
The manufacturer filed it against 4 model years across 2 brands (Chevrolet and GMC): 2020 Chevrolet Silverado 2500HD, 2020 Chevrolet Silverado 3500HD, 2020 GMC Sierra 2500HD, 2020 GMC Sierra 3500HD. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.