Toyota bulletin T-TT-0678-21 Rev
What it saysTT: Some 19CY LG DCM equipped vehicles may not be able to complete the firmware update due to not having an active account or waived services during the trial. NHTSA’s full summary ↓
Toyota filed this with NHTSA as a service bulletin dated Oct 10, 2023, received Jan 18, 2022, about the electrical system — 3 documents under this number: T-TT-0678-21 and 2 more. It names 21 model years (2020–2023). 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.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationTT: Some 19CY LG DCM equipped vehicles may not be able to complete the firmware update due to not having an active account or waived services during the trial. Follow the steps below to enable ?Temp DCM Activation?.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| T-TT-0678-21 Rev | Service bulletin | Oct 10, 2023 | 10245454 | not found |
| T-TT-0678-21 Rev | Service bulletin | Dec 15, 2022 | 10230371 | not found |
| T-TT-0678-21 | Service bulletin | Dec 20, 2021 | 10206530 | not found |
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.
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Model years it names
Source: as the manufacturer filed themAlso filed against model years this site has no page for: 2021 Toyota Redundant Sienna; 2022 Toyota Redundant Sienna; 2021 Toyota Redundant Venza; 2022 Toyota Redundant Venza.
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 17 model years this bulletin names have filed 2,808 complaints with NHTSA since 2015. 422 of them name 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 2020 Toyota RAV4, the 50 owners who gave an odometer reading for Electrical System reported it at a median of 3,023 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 owns a 2021 Toyota Rav4 Hybrid. The contact stated that on two separate occasions, while driving at high rates of speed, the vehicle stalled after slamming on the brake pedal. The contact waited approximately 20-30 seconds after the initial failure before being able to restart the vehicle and resume normal driving operation.
2021 Toyota RAV4 · Electrical System · filed with NHTSA Jan 26, 2024 · ODI 11568053
The contact owns a 2021 Toyota Sienna Hybrid. The contact stated that the vehicle was experiencing inaccurate fuel gauge readings. The contact stated while starting the vehicle, the fuel gauge reading displayed that the fuel tank was empty; however, while the contact was attempting to refuel the vehicle at the gas station, she became…
2021 Toyota Sienna · Electrical System · filed with NHTSA Jun 24, 2024 · ODI 11596197
The contact owns a 2021 Toyota Camry. The contact stated that while attempting to park her vehicle in her apartment complex parking lot, her vehicle continued to lurch forward without warning despite multiple attempts to stop. Due to the failure, the contact hit a gate as the vehicle continued to independently accelerate.
2021 Toyota Camry · Electrical System · filed with NHTSA Apr 18, 2022 · ODI 11461190
In depth: 2020 Toyota Camry electrical problems → · 2020 Toyota RAV4 electrical 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 electrical system
Source: same model, same component group59 other manufacturer communications filed against these Toyota models under the same component group (electrical system), newest first. The eight newest are listed; the rest are on the Toyota list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| T-SB-0050-26 | Over-the-air update | Aug 19, 2026 | A head unit software update (version 8612G42397) is now available for 2026 model year RAV4 Hybrid, and RAV4 Plug-in Hybrid vehicles via OTA… |
| T-TT-0803-26 | Service bulletin | May 21, 2026 | Some 26MY RAV4 HV/PHV vehicles with HU (head unit) versions 1136 or older may exhibit one or more of theintermittent conditions below: • No… |
| T-TT-0800-26 | Service bulletin | May 20, 2026 | Some 2026 RAV4 HV vehicles may display a Distance to Empty (DTE) that is higher than expected at initial fill-up. The DTE is computed using… |
| 22TE09 | Warranty extension | May 14, 2026 | Although the HV Floor Under Wire Harness and Rear Traction Motor Cable is covered by Toyota’s New Vehicle Limited Warranty for 3 years or 36… |
| T-SB-0029-26 | Over-the-air update | Apr 24, 2026 | A new head unit software update is available for 2023 – 2024 model year RAV4, RAV4 Hybrid, and RAV4 Prime vehicles equipped with Toyota Mult… |
| T-TT-0798-26 | Service bulletin | Feb 4, 2026 | Some systems such as remote engine start and remote door lock/unlock may be inoperative if they are not enabled/registered after ECU replace… |
| T-SB-0106-22 OBSOLETE | Service bulletin | Jan 30, 2026 | OBSOLETE NOTICE January 30, 2026: This bulletin is now obsolete. Please see T-SB-0001-26. |
| T-SB-0001-26 | Service bulletin | Jan 28, 2026 | Some 2018 – 2024 model year Toyota vehicles equipped with a Premium Audio with Dynamic Navigation System require a Special Service Tool… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Toyota, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Toyota T-TT-0678-21 Rev 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 T-TT-0678-21 Rev 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 Toyota warranty extension on file lists the ones Toyota has filed.
Which vehicles does T-TT-0678-21 Rev cover?
The manufacturer filed it against 21 model years: 2022 Toyota Avalon, 2021 Toyota Avalon, 2022 Toyota Camry, 2021 Toyota Camry, 2020 Toyota Camry, 2023 Toyota Corolla and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.