GM bulletin 21-NA-166
What it saysThis informational bulletin provides information on the turn signal stalk not cancelling and/or mis cancelling. NHTSA’s full summary ↓
GM filed this with NHTSA as a service bulletin dated Apr 15, 2025, received Apr 29, 2022, about the electrical system — 4 documents under this number. It names 56 model years across Chevrolet, GMC and Cadillac (2020–2025). 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 · Cadillac.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThis informational bulletin provides information on the turn signal stalk not cancelling and/or mis cancelling.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 21-NA-166 | Service bulletin | Apr 15, 2025 | 11019325 | PDF, 125 KB |
| 21-NA-166 | Service bulletin | Sep 17, 2024 | 11009099 | PDF, 123 KB |
| 21-NA-166 | Service bulletin | Sep 5, 2023 | 10242936 | PDF, 488 KB |
| 21-NA-166 | Service bulletin | Apr 11, 2022 | 10210545 | PDF, 67 KB |
What the document itself lists
Labour operation and the time the manufacturer allows
| Operation | Description | Time |
|---|---|---|
| 7480018 | Replace Turn Signal Switch and Bracket | 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.
Doing the repair yourself, or pricing it before the shop does? Search the part by fitment on eBay Motors — the listing and the price are the seller’s.
Find the turn signal for the 2025 Silverado →Affiliate disclosure: some links on this page are affiliate links. If you request a quote or buy through them we may earn a commission at no extra cost to you. Nothing on this page changes because of it.
Model years it names
Source: as the manufacturer filed themChevrolet 28 model years
GMC 23 model years
and 11 more on this site: 2025 GMC Sierra 3500HD, 2024 GMC Sierra 3500HD, 2023 GMC Sierra 3500HD, 2022 GMC Sierra 3500HD, 2021 GMC Sierra 3500HD, 2020 GMC Sierra 3500HD, 2025 GMC Yukon, 2024 GMC Yukon, 2023 GMC Yukon, 2022 GMC Yukon, 2021 GMC Yukon.
Cadillac 5 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 56 model years this bulletin names have filed 10,663 complaints with NHTSA since 2015. 1,901 of them name Electrical System, Steering, Exterior Lighting — 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 2020 Chevrolet Silverado, the 33 owners who gave an odometer reading for Electrical System reported it at a median of 7,300 miles. That figure is one model year’s, not the whole range this bulletin covers — medians from different model years are not averaged.
I rely heavily on this vehicle for my business and within 1 year of ownership, the vehicle broke down on the highway allowing it to only run @ 30mph. After finally locating a dealer who could evaluate the vehicle in less than 1 week, I was informed that the part was unavailable and they indicated, "it could take 1 month or 3 months to…
2023 GMC Sierra 2500HD · Electrical System · filed with NHTSA Jun 6, 2025
The contact owns a 2024 GMC Sierra 3500. The contact stated while driving at approximately 60 MPH and towing a Forest River Riverstone Legacy 5th Wheel trailer, the brake pedal was depressed to slow for oncoming stopped traffic; however, the vehicle failed to respond as needed with the “Service Trailer Brake” warning light illuminated.
2024 GMC Sierra 3500HD · Electrical System · filed with NHTSA Jul 9, 2025
Electrical components are failing in the tailgate lock/unlock mechanism. The tailgate goes up and down on its own while in park. It will also go up and down on its own after the truck is off and unattended This started happening about a week ago. It is available for inspection upon request and has not been inspected by any agency yet.
2021 Chevrolet Silverado 3500HD · Electrical System · filed with NHTSA Nov 27, 2024
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 electrical system
Source: same model, same component group314 other manufacturer communications filed against these GM models under the same component group (electrical system), newest first. The eight newest are listed; the rest are on the Chevrolet list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| N252529080 | Service campaign | Apr 1, 2026 | Service Update. Certain vehicles listed above may be missing a high voltage header plug on the RESS battery pack drive motor connector. Dea… |
| N252515590 | Service campaign | Jan 27, 2026 | Certain vehicles listed above, may have a condition in which the body-to-chassis ground strap may be corroded. Dealers will replace the grou… |
| 18-NA-180 | Service bulletin | Sep 4, 2025 | This Warranty Administration service bulletin provides Lithium-Ion battery Exchange Process and Transaction Submission information. |
| 25-NA-021 | Service bulletin | Jun 7, 2025 | This technical bulletin provides repair information to correct a customer concern of Radio Software Update W23E-178.1.2-M174-SQBR6-93.3. |
| 22-NA-083 | Service bulletin | May 17, 2025 | This service bulletin provides Requirements for Replacement of the Dual Mode Cord Set Under Warranty. |
| 23-NA-151 | Service bulletin | May 16, 2025 | This service bulletin and criteria within are to determine the internal state of the High Voltage Battery and core return shipping method. |
| PIE0753I | Service bulletin | May 15, 2025 | This engineering information (EI) will assist GM to recover a small number of electric vehicle battery packs from customer-owned vehicles in… |
| 25-NA-044 | Service bulletin | May 14, 2025 | This service bulletin provides information for dealers/technicians on SPS2 Hybrid/EV Battery Data Retrieval for Service High Voltage DTCs. |
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 21-NA-166 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-166 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-166 cover?
The manufacturer filed it against 56 model years across 3 brands (Chevrolet, GMC and Cadillac): 2025 Cadillac Escalade, 2024 Cadillac Escalade, 2023 Cadillac Escalade, 2022 Cadillac Escalade, 2021 Cadillac Escalade, 2025 Chevrolet Silverado and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.