GM bulletin 21-NA-139
What it saysThis service bulletin provides a repair procedure to correct a customer concern of a Malfunction Indicator Lamp (MIL) Illuminated - DTC P3055 Set. NHTSA’s full summary ↓
GM filed this with NHTSA as a service bulletin dated Apr 2, 2025, received May 1, 2025, about the engine. It names 49 model years across Chevrolet, GMC, Buick and Cadillac (2017–2021). 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 provides a repair procedure to correct a customer concern of a Malfunction Indicator Lamp (MIL) Illuminated - DTC P3055 Set.
Trouble codes it names: P3055
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 21-NA-139 | Service bulletin | Apr 2, 2025 | 11017443 | PDF, 127 KB |
What the document itself lists
Part the bulletin names
| Part number | Description | Qty | Find it |
|---|---|---|---|
| 13510484 | — | 1 |
Labour operation and the time the manufacturer allows
| Operation | Description | Time |
|---|---|---|
| 5080318 | Inspect For Mis-Configured DC/DC Converter | 1 hrs |
Read by machine from the document NHTSA serves (2 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 18 model years
GMC 7 model years
Buick 12 model years
Also filed against model years this site has no page for: 2020 Buick Lacrosse.
Cadillac 12 model years
and 4 more on this site: 2019 Cadillac XT5, 2018 Cadillac XT5, 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 48 model years this bulletin names have filed 10,160 complaints with NHTSA since 2015. 5,698 of them name Engine, 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.
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.
I was driving on express way 96W Left lane busy 5 o'clock traffic Car just died it was stop n go I could have been killed if it wasn't for a man that stopped behind me he couldn't help another person stopped and push the car in N To a grass area where at least I wouldn't be smashed in Called 911 state police inform help van He didn't…
2020 Chevrolet Blazer · Engine · filed with NHTSA Oct 25, 2023
While driving on the highway my truck started to buck and had a loud engine knocking noise. Speed was greatly reduced so much so that I was going under 45 mph in a posted 65. The check engine light did not come on. While sitting on the side of the highway there was a severe engine knock only when the revs on the engine were increased.
2021 GMC Sierra · Engine · filed with NHTSA Sep 9, 2021
The contact owns a 2018 Gmc Acadia. When the contact turned off the vehicle and removed the key from the ignition, the vehicle's warning sensor went off, the radio remained on, and the automatic door locks failed. As a result, the contact was unable to lock the vehicle. The vehicle was not repaired. The manufacturer was not notified.
2018 GMC Acadia · Electrical System · filed with NHTSA Jul 15, 2019
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 group246 other manufacturer communications filed against these GM models under the same component group (engine), newest first. The eight newest are listed; the rest are on the Chevrolet list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| N262570770-02 | Service campaign | Sep 25, 2026 | Certain vehicles may have a condition in which the thermal break tabs induce stress into the radiator causing a coolant leak. Dealers are to… |
| N262570770-01 | Service campaign | Sep 18, 2026 | Certain vehicles may have a condition in which the thermal break tabs induce stress into the radiator causing a coolant leak. Dealers are to… |
| N262570770 | Service campaign | Sep 15, 2026 | Certain vehicles may have a condition in which the thermal break tabs induce stress into the radiator causing a coolant leak. Dealers are to… |
| N262568830 | Service campaign | Aug 4, 2026 | Certain vehicles listed above may have a condition in which the oil filter was not adequately tightened. Dealers are to check and tighten th… |
| N262546590-01 | Service campaign | Jul 15, 2026 | Certain vehicles listed above, may have a condition where coolant leaks from the radiator hose quick connect at the radiator inlet. This sp… |
| N262548050 | Service campaign | Apr 24, 2026 | Certain vehicles, may have a condition that could cause the Catalytic Converter to fail. If this failure occurs, the Malfunction Indicator L… |
| N252540910 | Service campaign | Feb 25, 2026 | Service Update. Certain vehicles listed above may have a condition in which a quality issue with the engine was identified. Dealers will re… |
| N252494003-02 | Service campaign | Jan 21, 2026 | Certain vehicles listed above, may have a condition where the connecting rod and/or crankshaft engine components in these vehicles may have… |
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 21-NA-139 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-139 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-139 cover?
The manufacturer filed it against 49 model years across 4 brands (Chevrolet, GMC, Buick and Cadillac): 2021 Buick Enclave, 2020 Buick Enclave, 2019 Buick Enclave, 2018 Buick Enclave, 2017 Buick Enclave, 2019 Buick LaCrosse and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.