Gran Turismo Sport is a game that relies heavily on being online to play in certain activities in the game. It’s also a game that looks like it’s going to have both sporadic outages and regularly scheduled maintenance.
Right now the game does feature a news ticker that you can see on the main menu screen that will notify you of downtime, but there’s also a site dedicated to notifying users of both scheduled downtime and unexpected outages. You can check the status of GT Sport servers here.
The server status for GT Sport can be found here and are labeled with different color coded icons. Purple shows server maintenance, while blue items could be service interruption or unexpected server outages for GT Sport.
Polyphony has been updating users regularly through this news site, which does appear to be directly connected to through the PS4 browser functionality on the game’s dashboard. Using the image below you can see the location in game where you can check on the latest server updates. The box in the lower left corner of the main menu screen is the location of outage and maintenance notifications.

Knowing when maintenance in GT Sport is going to happen is important for players and hopefully Polyphony continues to do a good job of notifying players as a lot of the game is tied to an online connection to earn credit for races and participate in the Sport mode. During maintenance for GT Sport or during outages online features and Sport Mode are unavailable whether you’ve already begun a race during that time, or not.