After months of speculation and ongoing issues with Full Self-Driving (FSD), Elon Musk has admitted that many existing Teslas may never support it.

Millions of existing Teslas are powered by the company’s HW3 computers. According to Electrek, Musk finally admitted in a quarterly results call what the outlet has been saying for nearly a year, namely that the HW3 is not capable of supporting FSD.

We are not 100% sure. HW4 has several times the capability of HW3. It’s easier to get things to work on HW4 and it takes a lot of efforts to squeeze that into HW3. There is some chance that HW3 does not achieve the safety level that allows for unsupervised FSD.

The underlying issue is that the HW3 only has two NN nodes. While one was originally supposed to be there for redundancy, but Tesla has been using both in an effort to make FSD work the way its supposed to. Unfortunately, as Electrek points out, in order achieve level 4-5 autonomy, the vehicle must have a redundant node. As a result, it seemed clear for some time that the HW3 cannot deliver on Tesla’s promise of true FSD.

Musk tried to reassure investors that HW3 computers could be replaced, and that Tesla would do it for free.

If that turns out to be the case, we will upgrade those who bought HW3 FSD for free. And we have designed the system to be upgradable.

Unfortunately, the reality is not so straightforward. The physical design of the HW4 is considerably different than the HW3, meaning it many not be physically compatible with existing vehicles.

The admission is a big deal for Tesla, and underscores the issues the company is having delivering on Musk’s promise of true FSD—despite the many advances the company has made. Until the HW3 problem is resolved, millions of existing Tesla drivers may be out of luck.