Tesla HV battery pyro fuse: why it fires at DC chargers and what a replacement costs

What the part is and where it sits

The pyro fuse, also called the pyrotechnic fuse, sits in the power circuit of the high-voltage battery. Inside is a pyrotechnic charge: on command it tears the busbar apart instantly and the battery stops feeding the car. The part works once. After it fires it is replaced as a whole.

On cars from 2017 onwards the pack has service hatches in its floor, and the pyro fuse is reached without dropping the battery: on a lift, take out the low-voltage battery and the service disconnect, open the hatch, two bolts. About fifteen minutes of actual work (#453771). On earlier cars, where the pyro fuse lies on top of the pack, there is no quick route and the battery has to come down.

Why it fires when you unplug from a DC charger

May and June 2026 brought a run of identical stories into the chat: the shot happens at the moment the DC connector comes out of the port. A Model Y 2022 at BatteryFly station no. 362 in Borovlyany. The owner pressed “stop” in the Tesla app, pulled the connector straight away and heard a click. After that the car would not wake, the screen showed “low-voltage battery discharging, open doors manually”, and the tow truck cost 150 BYN (#449971, #450304).

The prevention comes from people who have already paid for the lesson: after you stop the session, wait about thirty seconds for the station to actually drop the current, and only then pull the connector. “Once you’ve disconnected, I’d wait another 30 seconds or so for the station to catch up that it’s off” (#450336).

How to tell it was the pyro fuse

The picture is recognisable: a click as you unplug, after which the car does not wake, the low-voltage system hangs on the 12V battery and runs it flat, and the doors open from inside with the mechanical handle. The symptoms overlap with a dead 12V battery (see 12V battery and bricking), so guessing in the yard gets you nowhere: a shop reads the codes and looks at the power circuit. Diagnostics around Minsk costs 35 BYN (#450341).

Codes from Service Mode are worth having in hand beforehand, and the decoding is collected in the BMS error code hub. If the high-voltage side still refuses to come up after the replacement, the next candidate to check is an isolation fault.

The “schedule a pyro fuse replacement” message

This story has nothing to do with the shot. There were two revisions of the pyro fuse. The first carries its own internal battery with its own expiry date, and once it passes the car starts asking for a replacement; this was seen first-hand on a Model S 2018 (#453764, #453765). The pyro fuse itself still works.

What makes a flat internal battery a problem: the pyro fuse may fail to fire in a crash, which is exactly when it is needed. The chat also carries the opposite version, about a spontaneous shot. Nobody has confirmed that one, and the message is still worth acting on.

The owner has these options:

1. Replace the battery inside the pyro fuse. Not worth the money.
2. Reset the date with Toolbox. The car goes quiet and safety gets quietly set aside.
3. Fit the second revision, which is powered from the high-voltage battery, part number 111131300E (#453775). It has no internal battery with an expiry date any more.

What to do on the spot

The car is dead, so the doors open from inside with the mechanical handle, which is what the screen tells you. Jump-starting the 12V battery gets you nothing: while the power circuit is broken, the high-voltage battery will not pick up the low-voltage system. After that it is a tow truck to a shop that works on HV batteries (service directory).

While you wait for the tow truck, write down the station number, the time and what the screen showed before and after the click. It saves the shop a round of questions, and it helps you see whether the same station keeps doing it.

What the replacement costs

Belarusian prices, summer 2026 (#450341):

1. Replacement at a shop, 750 BYN.
2. A 936 BYN work order for a Model 3 2021 owner.
3. Around 300$ all-in for a third owner.

What makes up the bill: diagnostics 35 BYN, software unlock 100$, replacement labour 80$, and the used original pyro fuse itself around 80$. Before you agree to a figure, ask the shop what it covers: the part, the unlock, the labour.

Where to get the part

In the summer of 2026 the original jumped in price. The cost to a shop in Warsaw went from 80$ to 120$: “The shop cost of a pyro fuse in Warsaw has risen to 120$” (#450310). With delivery to Belarus that becomes 130-140$ and up, and at those numbers suppliers stopped bringing it in (#450312). What is left on the market is China.

There is a serious reason to be careful with a Chinese part: a bad pyro fuse can “bury the whole penthouse”, meaning it takes the power box on the pack down with it (#450413). If there is no alternative, buy from a seller with a track record and carry the part to the shop yourself, so it is fitted in front of you (#450428). For numbers and catalogues see Tesla part numbers.