Exclusive: What Tesla is Changing to Improve Sentry Mode Efficiency

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Tesla recently rolled out power efficiency improvements to its Sentry Mode feature for the Cybertruck with software update 2024.38.4. These updates drastically improve the vehicle’s power consumption when Sentry Mode is active.

We’ve now uncovered more details on how Tesla achieved such drastic improvements in the vehicle’s power consumption, which Tesla estimated to be a 40% reduction.

Tesla made architectural changes to how it processes and analyzes video — optimizing which components handle which tasks. While the Cybertruck is the first to benefit from these advancements, Tesla plans to extend these upgrades to other vehicles in the future.

Sentry Mode Power Consumption

Tesla vehicles feature two main computers: the MCU (Media Control Unit) computer, which powers the vehicle’s infotainment center, and the FSD computer, which is responsible for Autopilot and FSD. Both of these computers remain on and powered any time the vehicle is awake, consuming about 250-300 watts.

Typically, the vehicle only uses this power while it’s awake or actively driving. It’s not a major concern since the car automatically goes to sleep and shuts down its computers after about 15 minutes of inactivity. However, the larger issue is that these computers also need to remain on when Sentry Mode is active, causing a 250-watt draw whenever Sentry Mode is on.

Interconnected System

Today, the vehicle’s cameras are connected to the FSD computer, which connects to the MCU, which is finally connected to the USB ports. Because of this interconnected setup, everything needs to remain powered. Footage needs to be streamed from the FSD computer into the MCU, where processes like motion detection occur. The data then needs to be compressed before finally being written to the USB drive. That’s a lengthy process, requiring multiple computers to remain on in order to be able to record and save live video.

Architectural Changes

Tesla is making some architectural changes to address Sentry Mode’s high power consumption by shifting the responsibilities of the vehicle’s computers. By shifting motion detection and possibly the compression activity to the FSD computer, Tesla will now be able to keep the MCU computer asleep. The MCU is still required to push the video to the USB drive, but Tesla can now wake up the system only when it’s needed.

For instance, the FSD computer will still handle the connection to the vehicle’s cameras, but it will now also detect motion. When that Sentry event occurs, it can wake up the MCU to write the data to the USB drive and then have it go back to sleep.

This approach ensures the MCU isn’t continuously powered to analyze and compress video, instead activating it only when data needs to be written.

Processor Isolation & Task Allocation

Tesla’s current architecture separates the Autopilot Unit (APU) from the MCU. This is done for several reasons - but first and foremost is safety. The MCU can be independently restarted even mid-drive without impacting the APU and key safety features.

Additionally, by isolating the APU from the MCU, tasks that are optimized for each unit—processing versus image transcoding—can be offloaded to the processing unit that’s better suited for it. This helps keep both the APU and MCU operating at their optimal power and performance parameters, helping to manage energy consumption more efficiently.

Kernel-Level Power Management

Tesla’s been working on more than just FSD or new vehicle visualization changes and has been putting in the effort to optimize the operating system’s underlying kernel. While not in heavy use, Tesla is underclocking the processors of both the MCU and APU, reducing power usage and heat generation.

Of course, other kernel optimizations and programming tricks, such as the ones Tesla uses to optimize its FSD models, also factor into the increased overall efficiency of the vehicles.

Additional Benefits

Since Tesla vehicles also include a Dashcam that processes video, it’s possible we may also see these additional power savings whenever the vehicle is awake. This could also affect other features, such as Tesla’s Summon Standby feature, which keeps the vehicle awake and processing video to give users almost instant access to the vehicle’s Summon feature.

Roll Out to Other Vehicles

While the Cybertruck was the only vehicle to receive these power improvements to Sentry Mode, we were told that they’re coming to other vehicles too. Tesla is introducing these changes with the Cybertruck first, leveraging its smaller user base for initial testing before expanding the rollout to other vehicles.

USB Port Power Management

To further conserve energy and reduce waste, Tesla now powers down USB ports, even if Sentry Mode is active. This change has impacted many users who rely on 12v sockets or USB ports to remain powered to keep accessories such as small vehicle refrigerators on.

It’s not immediately clear whether these changes to Sentry Mode impact this change or whether power to 12v outlets was removed strictly due to safety concerns.

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Tesla Releases FSD V12.6.1 for Model 3 & Model Y

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Last night, Tesla released software update 2024.45.25.15, which includes FSD V12.6.1. This update adds support for all HW3 vehicles, including the Model 3 and Model Y. We’re excited to see the continued support for HW3 owners. 

FSD V12.6.1

V12.6.1 is now going wide, according to Ashok Elluswamy, Tesla’s VP of AI. This update is going to the Model 3 and Model Y for the first time - as only the Model S and Model X were included in FSD V12.6. 

V12.6 is a big step forward for HW3 - it includes End-to-End on Highway, Improved City Streets Behavior, and Smoother and More Accurate Tracking - all contributing towards a better, smoother, and more comfortable build of FSD. You can read our comparison between FSD V12.6 and V13.2.2 here. 

In short, FSD V12.6 performs considerably closer to V13 than V12.5.4.2 - which is a massive improvement. It performs as well as the Cybertruck version of FSD V13, which is still missing a few features when compared to other HW4 vehicles, but it’s a great sign for HW3. A lot of the improvements can be pointed to in the improvements to lane selection and decision-making - the vehicle tends to hesitate far less on V12.6, meaning the ride is a lot smoother. Many early V12.6 testers mentioned that it felt more like V13-mini than anything else.

Legacy Model S & X

We haven’t seen this update hit any legacy Model S and Model X vehicles just yet. We’re not sure whether Ashok’s statement of “generally” applies here - but it should. If you do get the update, please let us know.

Legacy Model S and Model X vehicles are still on an older FSD build and potentially won’t see another FSD update for a little while longer. While they do have the same FSD hardware as other vehicles, there are enough hardware differences that require a build specifically for these vehicles.

Release Date

FSD V12.6.1 is going out now to the redesigned Model S and X with HW3 and all Model 3 and Model Y vehicles with HW3. The initial wave went out last night, and we expect to see more later today or tomorrow. If this release ends up going “wide,” we should see much larger waves go out next week.

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Tesla Issues Physical & OTA Recall for Hardware 4 Computer

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Tesla has issued a recall for some vehicles due to issues linked to a revision of the Hardware 4 (HW4) computer that was introduced this past November. This recall affects all vehicles with the revised hardware except for the Cybertruck, as it uses a slightly modified version of the HW4 system.

Many vehicle owners have reported a complete failure of their Autopilot computer, which not only leaves the vehicle without FSD and Autopilot but also disables many of the active safety features that make a Tesla what it is.

Let’s take a look at this recall - because the recall is partially physical and partially a software recall.

HW4 Failure

Tesla has identified the failure and flagged it to the U.S. NHTSA (but not Transport Canada or Euro NCAP at the time of publishing) as a recall.

Tesla mentions that the vehicle’s FSD computer circuit board may short circuit, resulting in the loss of the rearview camera image. The recall itself is focused on the rearview camera - as not having a functional rearview camera breaks a Federal Motor Vehicle Safety Standard. However, it does impact more than just the rearview camera.

As previously mentioned, users have experienced the full loss of Autopilot and FSD on these vehicles, as well as reduced traction control and removal of safety features such as automatic emergency braking, collision avoidance assist, and forward collision warnings. 

While the vehicle remains driveable, it is not necessarily a good idea to drive the vehicle with many of these features, especially with the reduced traction control noted by many people. We’ve already noted that while Tesla has been sending tow trucks to pick up some vehicles, it is also prompting owners to drive the vehicle to their service center in some cases.

Remedy

Unlike most of Tesla’s recalls, this one isn’t entirely an OTA recall, owing to the fact that people have already experienced circuit board shorts and are already waiting for replacements.

The software portion of the recall has already been mostly completed for any vehicles with Tesla software update 2024.45.25.3 or greater. However, a significant portion of the tracked fleet remains on update 2024.44.25.2 (approximately 20%), so we recommend updating your HW4 vehicle whenever you receive the notification.

On the hardware side, Tesla is immediately identifying and replacing hardware that has had circuit board failure. Tesla is also reaching out to customers who have expressed intermittent issues with Autopilot features, active safety features, or vehicle cameras that don't display correctly. If you have experienced any of these issues in a late 2024 vehicle, we recommend submitting a service ticket with Tesla to ensure that your vehicle isn’t affected by this recall.

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