Modem and bands: USA vs Europe. Replacement and SIM

Summary

• NA/EU LTE bands differ, which is why cars brought in from the USA have an unstable connection: in some locations the track stutters several times because the signal drops (#497795).
• An American modem in Belarus picks up LTE only; the European and global ones add 3G (#465340, #470186).
• Newer cars (a 2025 Juniper, for example) have a global modem: coverage is fine with any Belarusian carrier, and MTS gets a signal even in an underground car park (#497797, #497798).
• The fix for an American car is replacing the modem with an EU/global one plus a correctly fitted and activated physical SIM.

A car's region cannot be changed: it is a secure config. Only the navigation map region and the account region change, while for Tesla's servers an American car stays American forever and keeps receiving NA updates (#500631, #500633).

The misconception: “our carriers support eSIM, just load the profile”

The most common piece of wrong advice about in-car connectivity. It does not work:

• A Tesla has an M2M SIM, not a consumer eSIM. A carrier profile cannot be loaded into it (#451584, #451587, #451589).
• The eSIM is soldered into the modem and belongs to Tesla, and Tesla has no mechanism for writing another eSIM. Connecting a Belarusian or any third-party eSIM to an American car is impossible in principle (#487237, #487244, #486079).
• The mirror situation: an American modem with an eSIM does not work in Europe; there, too, only a physical SIM saves the day (#476567, #487252). A Japanese modem in Europe requires roaming restrictions on the eSIM to be lifted separately (#476569).
• A European modem on an eSIM is useless in Belarus as well: it is designed for the EU (#487253).

There is one route: a physical SIM. Everything else people offer to “load” is inapplicable to the car.

The physical SIM: fitting and activation

1. Prepare the SIM before fitting it (see the section on tariffs); getting it out afterwards is awkward.
2. Put the card into the slot of the telematics unit. On Model 3/Y it is under the roof, on S/X it depends on the car (#497815).
3. Switch the car from the eSIM to the physical SIM via Toolbox. This is a mandatory step on all non-Chinese cars; on Chinese ones it is not required (#470184, #470083).
4. Check the result: Service Mode → Infotainment → Connectivity, bottom right. The line Valid SIM — eSIM means the switch did not happen (#470183, #470116).

The cost of the work as of September 2026 is from $30 (2024 Model Y) to $50 at a shop, and the procedure itself takes 5–10 minutes (#452948). Switching back to the eSIM before a trip to the EU is also done through Toolbox, but it does not work on every car and only with active premium (#497814, #496679).

The classic fault: “picks up the network for a second and loses it”

The symptom looks like a modem or carrier problem, but the cause is more often the card itself:

• The SIM deforms or melts from the heat inside the unit, or gets scratched by the contacts. The chat's diagnosis is blunt: a warped or scratched SIM means replacement, full stop (#489533, #484777).
• On Highland the card moved up under the roof, into the hottest spot, and in hot countries it melts (#489526, #489536).
• The fix is replacing the SIM plus a SIM extender that brings the card into the cabin. In the chat people use two different GSMIN DS8 extenders in series; for one owner it has been working for a fourth year (#489599, #489657).
• If Autopilot temperatures are rising at the same time, look deeper: that may be a symptom of a bigger problem.

How much data the car needs

As of September 2026:

• With active Premium Connectivity, 15 GB/month is comfortably enough, including YouTube. For heavy users (constant streaming, video while parked) it is tight.
• Without premium, 1–2 GB is enough: maps, notifications, the app and the certificates remain.
• The chat names MTS “Internet mini” and life:) “Bezlimit Lite” (13.9 BYN) as working plans; 8–15 GB is comfortably enough (#451369, #470084).

What the data allowance does not cover: the car does not download firmware over the SIM at all, and the EU maps weigh about 8 GB per load; both of those are Wi-Fi only. The breakdown is in the article on firmware and updates.

On premium, as of September 2026, two corrections:

• The “buy premium from a middleman for 200 BYN” scheme is dead. The fixers who did this have scattered; nobody is promising premium to anyone any more. If someone offers you such a service now, that is a way to lose money, not a way to get premium.
• Linking a car to the app has got stricter. Tesla verifies documents in every case (the registration certificate and the driving licence). Belarusian documents pass the manual review for the Polish region as long as the first and last name match in both. “Cat photos” and random addresses no longer get through. The procedure is in the article on adding a car to the app.

Why the SIM matters even without premium

The first argument is certificates: they only renew on a car that is online. A car standing for months without a connection risks losing its certificates and app access, and restoring them costs more than any tariff. Details and how to check: certificates and linking to the app and the risk calculator.

The second argument is wake-up. With a local SIM the standard tap on the car in the app often fails to wake it, and owners resort to workarounds: entering the car's SIM number on any site with registration so an incoming SMS wakes it; sending a pin from the phone's maps to the car; calling the number; poking around the tabs in the “Service” section (#451574, #451576, #451577). For some owners neither an SMS nor a call wakes it. After swapping the modem for one that picks up 3G, the car wakes on a tap (#500438, #500440).

Tariff and carrier: the traps

Carrier and hardware prices below are as of September 2026.

• MTS pushes paid subscriptions onto the car's SIM, and they cannot be cancelled through the web account: the confirmation code goes to the SIM that is lying under the roof. The right order is before fitting: disable the PIN, remove the paid subscriptions, ask the carrier to block them from being added, and set up access to the account (#457444, #457445, #457473).
• A1: tethering mode is not included in every plan. The symptom is the car's internet breaking up, and people start taking the car apart although the problem is the tariff plan. The option costs about 1.1 BYN/day (#456267, #456269).
• Unlimited plans cannot be put into the car directly: it peers and gets banned. A duplicate of such a SIM works fine in a modem or in ScreenMate (which is detected as an ordinary Android tablet) (#480109, #480110).
• The combination that works financially: a minimal plan in the MCU plus a proper unlimited plan on the phone with tethering. With constant tethering, some plans add a surcharge of about 1 BYN/day (#480120).
• An alternative to a SIM in the car is a modem with a battery, for example the Zyxel WAH7601 4G LTE (around 700 BYN on a marketplace, cheaper on classifieds), though its battery should not be relied on too heavily (#480130).

Roaming and trips to the EU

• A Belarusian physical SIM in the car does not work in roaming. Roaming lives on a handful of carriers, and there is physically nowhere in the car to select a network manually (#486079, #486082).
• Take the SIM out before the border. Formally the carrier should not charge more than 800 BYN, but the chat knows of bills of 5,000 and 8,000 BYN (#480734, #480736). On a written complaint they usually meet you halfway and knock off 20–50% (#480749). The reason for the bills: even with data transfer switched off, traffic goes out for registering on the 4G network, so a physical disconnect is more reliable (#480738).
• What works on a trip: tethering Wi-Fi from a phone with a local eSIM, or switching to the European KPN eSIM if it is in the modem's profile, through Toolbox right at the border (#486084). Of the travel eSIMs for tethering to the car, Airalo did not work out (the navigation map did not display), while eSIM.io performed fine (#486123).

A related problem on American cars: FM radio

A tuner with the American 0.2 MHz grid step does not take European frequencies on a 0.05 MHz step and picks up nothing below roughly 88 MHz:

• In Minsk, no American car can pick up “Radio Relax” on 87.5 (#477651, #477653), nor even-numbered frequencies such as “Avtoradio” on 98.0, confirmed by two owners (#465380, #465381).
• The honest fix is an EU modem plus a European radio unit, expensive and troublesome (#477657). The practical substitute is online radio through TuneIn or a phone over Bluetooth.
• On an NA→EU region change FM radio disappears for the same reason, and on top of that the Actually Smart Summon range collapses from roughly 86 m on NA maps to 6–8 m (#453864, #465391).

Cost

As of September 2026:

• An EU/global modem with fitting: from $200 (#470188, #460513); the full retrofit, depending on the model and the parts, is $200–450.
• Switching eSIM → physical SIM via Toolbox: $30–50, 5–10 minutes.
• A SIM extender is a consumable; budget the price of two GSMIN DS8 units.

Links

• Firmware and updates: why Wi-Fi is required
• Certificates and linking to the app
• Adding a car to the app and Premium Connectivity
• Certificate risk calculator
• A case of replacing a modem with an EU one: https://olegkutkov.me/2021/06/10/tesla-model-3-us-lte-modem-replacement-and-some-reverse-engineering/
• The Hackaday write-up: https://hackaday.com/2022/01/03/lte-modem-transplant-for-a-tesla-imported-into-europe/
• Official: the 3G→LTE transition: https://www.tesla.com/support/3g-cellular-network-retirement
• Discussion of modem bands: https://teslaownersonline.com/threads/lte-modem-specs-are-here.7218/