Acura bulletin B24040A
What it saysService News - Due to On-Board Diagnostic (OBD) regulation change starting with 2019 vehicles, American Honda’s Variable Valve Timing and Lift Electronic Control (VTEC) On-Board Diagnostic monitors are now included… NHTSA’s full summary ↓
Acura filed this with NHTSA as a manufacturer communication dated May 1, 2024, received May 15, 2024, about the engine. It names 14 model years (2019–2025). A manufacturer communication 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.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationService News - Due to On-Board Diagnostic (OBD) regulation change starting with 2019 vehicles, American Honda’s Variable Valve Timing and Lift Electronic Control (VTEC) On-Board Diagnostic monitors are now included in the EGR/VVT OBD Monitor Readiness status group. Due to some customer’s driving patterns, they may not drive in the fashion needed to operate the VTEC (EGR/VVT) that only operates above 5,350 rpm to run the OBD monitoring. Therefore, the EGR/VVT OBD monitor group readiness status is not set to “Complete” when the customer presents their vehicle to a Smog Check station for inspection.
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| B24040A | Other | May 1, 2024 | 11000147 | PDF, 87 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 themA 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 14 model years this bulletin names have filed 1,043 complaints with NHTSA since 2015. 339 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.
On the 2020 Acura MDX, the 22 owners who gave an odometer reading for Engine reported it at a median of 55,000 miles. That figure is one model year’s, not the whole range this bulletin covers — medians from different model years are not averaged.
Our Acura MDX has continued to have Auto Idle Stop issues since we purchased the vehicle. Sometimes the vehicle would not restart after being stopped at a traffic light. Most recently, an accident almost occurred when the vehicle stuck behind us at the traffic light tried to go around us while we were trying to get the engine started and…
2020 Acura MDX · Engine · filed with NHTSA May 23, 2023 · ODI 11523509
2004 MDX had digital screen problems where the screen remained black upon starting, which was hazardous as I couldn’t tell how fast I was going. After 3 visits to the dealership they identified the problem and fixed it Also, in a separate instance, car stalled after trying to start up after stop signs or while waiting in traffic several…
2024 Acura MDX · Engine · filed with NHTSA Mar 20, 2026 · ODI 11725842
The car does not restart after it has turned off during an idle stop. This is part of the start/stop system. The stop/start feature will leave you stranded at stoplights due to a failure to restart the car. To restart, you must put the car in Park mode and hit the start/stop button at least twice to turn it off, then turn on the car.
2019 Acura TLX · Engine · filed with NHTSA Nov 23, 2022 · ODI 11494676
In depth: 2025 Acura MDX engine problems → · 2020 Acura MDX engine problems → · 2019 Acura MDX 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 group29 other manufacturer communications filed against these Acura models under the same component group (engine), newest first. The eight newest are listed; the rest are on the Acura list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| BTI&05122026901 | Other | May 13, 2026 | Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2024-2026 MDXs with a client complaint of the Malfunction In… |
| BTI&04292026901 | Other | Apr 29, 2026 | Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2024-2026 MDXs with a client complaint of the Malfunction In… |
| BTI&04202026901 | Other | Apr 20, 2026 | Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2024-2026 MDXs with a client complaint of the Malfunction In… |
| BEBM12032025901 | Other | Dec 3, 2025 | Dealer Message - Under certain circumstances, after coming to a stop and the idle stop feature engages, the vehicle may not automatically re… |
| B25-048 | Service bulletin | Sep 17, 2025 | Service Bulletin - Oil leak at the cam chain tensioner inspection cover due to and insufficient sealant adhesion on the inspection cover. |
| BPS&08122025901 | Other | Aug 12, 2025 | Dealer Message - Acura is also implementing an additional (1) twenty-four (24) month period for 2015 model year Acura TLX vehicles, commenci… |
| BTI&07312025903 | Other | Aug 1, 2025 | Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2023-2025 MDXs with a client complaint of a no auto re-start… |
| BTI&07152025901 | Other | Jul 15, 2025 | Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2023-2025 MDXs with a client complaint of a no auto re-start… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Acura, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Acura B24040A a recall?
No. A manufacturer communication 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 B24040A 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 Honda warranty extension on file lists the ones Honda has filed.
Which vehicles does B24040A cover?
The manufacturer filed it against 14 model years: 2022 Acura ILX, 2021 Acura ILX, 2020 Acura ILX, 2019 Acura ILX, 2025 Acura MDX, 2024 Acura MDX and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.