GM bulletin 20-NA-203
What it saysThis informational bulletin explains how the regen works for the DEF system and how it works at different levels. NHTSA’s full summary ↓
GM filed this with NHTSA as a service bulletin dated Jul 17, 2024, received Oct 11, 2022, about the engine — 3 documents under this number. It names 38 model years across Chevrolet and GMC (2018–2025). 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.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThis informational bulletin explains how the regen works for the DEF system and how it works at different levels.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 20-NA-203 | Service bulletin | Jul 17, 2024 | 11005341 | PDF, 562 KB |
| 20-NA-203 | Service bulletin | Jan 25, 2023 | 10231499 | PDF, 181 KB |
| 20-NA-203 | Service bulletin | Sep 13, 2022 | 10222783 | PDF, 182 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 23 model years
Also filed against model years this site has no page for: 2019 Chevrolet 6500.
GMC 15 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 37 model years this bulletin names have filed 6,518 complaints with NHTSA since 2015. 3,694 of them name Engine, Electrical System, Fuel/Propulsion 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 2019 Chevrolet Silverado, the 143 owners who gave an odometer reading for Engine reported it at a median of 71,000 miles. That figure is one model year’s, not the whole range this bulletin covers — medians from different model years are not averaged.
The contact owned a 2024 GMC Sierra 2500 HD. The contact stated that after parking the vehicle at night and plugging in the engine block heater to a standard 110-Volt outlet with an extension cord; 15-minutes later neighbors were screaming to the contact to exit the residence because the vehicle had caught on fire, and the residence was…
2024 GMC Sierra 2500HD · Engine · filed with NHTSA Nov 25, 2024 · ODI 11627201
There is a common and very dangerous electrical wire routing problem on my vehicle, along with 3 dozen others and my dads (separate but same truck) i confirmed with (FB group for owners of 17-19 L5P GMC diesel trucks) where the alternator positive wire from the alternator to the battery is run right along and across a rather sharp part…
2019 Chevrolet Silverado 3500HD · Electrical System · filed with NHTSA Oct 29, 2025 · ODI 11696384
Multiple instances of diesel engine emissions system parts and software failure. While driving, towing or not, the DIC would randomly display a message that the DEF level is low and reduced speed will occur in x-amount of miles and that mileage would then begin a visible countdown on the DIC, sometimes much more quickly than the actual…
2021 GMC Sierra 3500HD · Engine · filed with NHTSA Nov 1, 2024 · ODI 11623109
In depth: 2025 Chevrolet Silverado engine problems → · 2024 Chevrolet Silverado engine problems → · 2024 Chevrolet Silverado electrical problems → · 2023 Chevrolet Silverado engine 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 engine
Source: same model, same component group189 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 |
|---|---|---|---|
| N262572131-01 | Service campaign | Oct 23, 2026 | Customer Satisfaction Program. Certain vehicles listed above may have a condition in which the oil galley in the cylinder head was not dril… |
| N262576260 | Service campaign | Oct 15, 2026 | General Motors has decided to conduct a Voluntary Emission Recall. Certain vehicles may have a condition that could cause a small exhaust le… |
| N262572131 | Service campaign | Aug 28, 2026 | Customer Satisfaction Program. Certain vehicles listed above may have a condition in which the oil galley in the cylinder head was not dril… |
| 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… |
| 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… |
| 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… |
| 25-NA-339 | Service bulletin | Nov 6, 2025 | Under Field Actions N252494000, N252494001, the service procedure includes performing a PICO test on vehicle engines within the identified s… |
| N252508341 | Service campaign | Sep 16, 2025 | Certain vehicles listed above, may have a condition that could cause the engine coolant control valve to fail an onboard vehicle diagnostic… |
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 20-NA-203 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 20-NA-203 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 20-NA-203 cover?
The manufacturer filed it against 38 model years across 2 brands (Chevrolet and GMC): 2025 Chevrolet Silverado, 2024 Chevrolet Silverado, 2023 Chevrolet Silverado, 2022 Chevrolet Silverado, 2021 Chevrolet Silverado, 2020 Chevrolet Silverado and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.