GM service campaign N252508350
What it saysCertain vehicles listed above, may have a condition that could cause the engine coolant thermostat to open at a lower temperature than intended. NHTSA’s full summary ↓
GM filed this with NHTSA as a service campaign dated Oct 21, 2025, about the engine. It names 4 model years across Chevrolet, GMC and Cadillac (2021). A service campaign 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.
One page for every brand it was filed under. Each brand’s bulletins: Chevrolet · GMC · Cadillac.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationPicked out of NHTSA’s summary below, word for word. The document itself is the record, and the dealer checks the VIN.
Certain vehicles listed above, may have a condition that could cause the engine coolant thermostat to open at a lower temperature than intended. If this condition were to occur, the Malfunction Indicator Lamp (Check Engine Light) will illuminate and a diagnostic trouble code will set. Additionally in some cases, the engine cooling fans may run after the engine is switched off. This special coverage covers the condition described above for a period of 15 years or 150,000 miles (240,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. For vehicles covered by Vehicle Service Contracts, all eligible claims with repair orders on or after October 21, 2025, are covered by this special coverage and must be submitted using the labor operation codes provided with this bulletin. Claims with repair orders prior to October 21, 2025, must be submitted to the Service Contract provider. Vehicle owners or lessees who paid for repairs referenced in this Special Coverage (“Customers”) are eligible for reimbursement of their reasonable and customary expenses in accordance with the procedures specified below. The conditional right to reimbursement is provided by GM solely in the interest of customer satisfaction and is personal to Customers. Customers may not assign and GM does not consent to any assignment of any Customer’s right to submit reimbursement claims, or to receive reimbursement, or any other rights granted by this Special Coverage to any third party, including but not limited to service contract providers, and this Special Coverage is not intended to and does not confer any third party beneficiary, subrogation or contribution rights, or any other rights to reimbursement, against GM, whether in law, equity or otherwise, on any third parties. Dealers are to replace the engine coolant thermostat as necessary. The repairs will be made at no charge to the customer.
Trouble codes it names: P0128 all 1 read from the document itself; NHTSA’s summary names none
One of the 432 warranty extensions and special-coverage programs on file — every make, with the term each runs to.
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| N252508350 | Service campaign | Oct 21, 2025 | 11024390 | PDF, 231 KB |
What the document itself lists
The manufacturer titles it “N252508350 - Special Coverage”.
Parts the bulletin names
| Part number | Description | Qty |
|---|---|---|
| 12741009 | HOUSING, ENG COOL THERM | — |
| 12623519 | SEAL, RAD OTLT PIPE (O RING) | — |
| 12648547 | SEAL, ENG COOL AIR BL PIPE (O RING) | — |
| 12648665 | SEAL, INT MANIFOLD | — |
| 12346290 | — | — |
| 10953464 | — | — |
Labour operations and the time the manufacturer allows
| Operation | Description | Time |
|---|---|---|
| 9900952 | Customer Reimbursement Approved -For USA and Canada dealers only -For Export dealers… | 0.2 hrs |
| 9900953 | Customer Reimbursement Denied – For USA dealers Only N/A ZREG ** Note: The above… | 20 hrs |
Read by machine from the document NHTSA serves (6 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.
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 1 model year
GMC 1 model year
Cadillac 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 339 complaints with NHTSA since 2015. 90 of them name 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.
I noticed a water sloshing sound behind the dash when first starting out for about a month. I didn’t get any warning lights or notice anything leaking under the car but when I checked under the hood the coolant reservoir was empty. I made appointment at GM dealership and they found I had a leak along the side seam of my radiator.
2021 Cadillac XT6 · Engine · filed with NHTSA Oct 20, 2026 · ODI 11772504
The contact owns a 2021 Chevrolet Blazer. The contact stated that the check engine warning light was illuminated. The contact was unable to use the electrical features in the vehicle. The vehicle was taken to the local dealer, where it was diagnosed that the purge pump needed to be replaced. The vehicle was not repaired.
2021 Chevrolet Blazer · Engine · filed with NHTSA Nov 28, 2023 · ODI 11557219
The contact owns a 2021 Cadillac XT5. The contact stated that while an oil change was being completed, an oil leak was discovered. No warning light was illuminated. The dealer diagnosed the vehicle and determined that the head gasket needed to be replaced. The vehicle was repaired; however, the failure recurred.
2021 Cadillac XT5 · Engine · filed with NHTSA Jun 11, 2026 · ODI 11743461
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 group99 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 |
|---|---|---|---|
| N262570770-03 | Service campaign | Oct 16, 2026 | Certain vehicles may have a condition in which the thermal break tabs induce stress into the radiator causing a coolant leak. Dealers are t… |
| 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… |
| 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… |
| N252502891 | Service campaign | Jul 16, 2025 | Customer Satisfaction Program. Certain vehicles listed above may have a condition in which the internal differential nut was cross threaded… |
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 and Cadillac, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is GM N252508350 a recall?
No. A service campaign 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 N252508350 repair free?
A service campaign 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 N252508350 cover?
The manufacturer filed it against 4 model years across 3 brands (Chevrolet, GMC and Cadillac): 2021 Cadillac XT5, 2021 Cadillac XT6, 2021 Chevrolet Blazer, 2021 GMC Acadia. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.