Tesla's app, which many owners use as a key for the vehicle, was down for hours Monday evening.
Several Tesla drivers took to Twitter complaining that the app was down and tagging Tesla with questions about when it would be restored.
One Pleasanton, California, woman told NBC Bay Area she had to take an Uber home because of the Tesla outage.
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Tesla owners also are issued a card that can be used as a key, but several indicated they rely on the app to get into and operate their vehicle and thus don't keep the card on them.
Downdetector.com indicated the outage started at about 4:30 p.m. and lasted for about four hours.
Tesla confirmed the mobile app was "briefly unavailable" Monday and was restored "soon after." Several users said it was 3-4 hours.
Tesla said it provides owners with a few options to locking, unlocking and starting their vehicles, including a physical key fob or key card, which the company has long encouraged owners to carry in case their phone dies, as well as the ability to use the Tesla mobile app. And Model 3 owners can use their phones as a key, the company said.
The Model 3’s phone-as-key function uses Bluetooth Low Energy to communicate with the vehicle, and thus full app functionality is not required to lock, unlock and start the car, Tesla said.
The phone-as-key functions separately from the in-app lock-unlock features, which require a cell signal and are not a primary means of entrance, exit and vehicle usage, the company said.
As a result, Tesla said there was no impact to phone-as-key functionality as long as users remained logged into their accounts.