The company said the driver, Wei Huang, 38, a software engineer for Apple, had received several visual and audible warnings to put his hands back on the steering wheel but had failed to do so, even though his Model X S.U.V. had the modified version of the software. His hands were not detected on the wheel for six seconds before his Model X slammed into a concrete divider near the junction of Highway 101 and 85 in Mountain View, and neither Mr. Huang nor the Autopilot activated the brakes before the crash.

The accident renews questions about Autopilot, a signature feature of Tesla vehicles, and whether the company has gone far enough to ensure that it keeps drivers and passengers safe.

“At the very least, I think there will have to be fundamental changes to Autopilot,” said Mike Ramsey, a Gartner analyst who focuses on self-driving technology. “The system as it is now tricks you into thinking it has more capability than it does. It’s not an autonomous system. It’s not a hands-free system. But that’s how people are using it, and it works fine, until it suddenly doesn’t.”

On Saturday, Tesla declined to comment on the California crash or to make Mr. Musk or another executive available for an interview. In its blog post on Friday about the crash, the company acknowledged that Autopilot “does not prevent all accidents,” but said the system “makes them much less likely to occur” and “unequivocally makes the world safer.”

For the company, the significance of the crash goes beyond Autopilot. Tesla is already reeling from a barrage of negative news. The value of its stock and bonds has plunged amid increasing concerns about how much cash it is using up and the repeated delays in the production of the Model 3, a battery-powered compact car that Mr. Musk is counting on to generate much-needed revenue.