Following the software bug that left cars crawling on the formation lap at the Bahrain / Malaysian GP, there's a fair bit of misinformation going round about how engine modes work. So let's dive in. Every car runs the same standard ECU, the central unit controlling the engine. It's made by Motion Applied, formerly McLaren Applied. Not the F1 McLaren. A different McLaren. The ECU is loaded with two separate sets of modes: the team's and the FIA's. The team's modes are their racing modes: qualifying, race, energy saving, recharge, "party mode", etc. The FIA's modes are safety modes: VSC, wet running, etc. Sunday's bug was in the wet-weather energy management, which cuts maximum electrical deployment from 350kW to 250kW in certain sectors. The FIA's software is developed together with the teams, and the same release goes to every competitor. Everyone runs identical safety modes, and everyone can see that they do. The only way to load or update modes is to physically connect a computer to the car via the umbilical and transfer the configuration to the ECU. No over-the-air updates, neither from the FIA or the teams. Which is exactly why Sunday's fix took time. The FIA issued updated software to all teams, and each team then had to install it on their own cars before the race could start. Nor can anyone remotely activate a mode. Modes are selected by the driver on the steering wheel. When a driver asks for more power, the team doesn't flip a switch. They tell him which combination of inputs gets him there. Same with the safety modes. If race control decides conditions call for one, it isn't a remote command that switches the modes. It's a message to teams and drivers to select it. Once a mode is active, the software in the car makes decisions by itself, such as limiting deployment sector by sector. That's what went wrong on Sunday. Code already in the car misbehaving, not someone in race control pressing a button. Tldr: Race Control doesn't have a remote control for engine modes.