The Formula 1 software bug at Sepang was a fault in the FIA’s standard power unit software that put several cars into a 60-second emergency lockdown during the wet formation lap for the 2026 Bahrain Grand Prix in Malaysia on October 4, 2026. A wet-weather setting that caps electrical deployment at 250kW, combined with the near-walking pace behind the Safety Car, very low engine speeds, low grip and the way Sepang’s Turn 9 sector is configured, tricked the system into thinking a team was deliberately switching off its MGU-K. The failsafe cut both electric and combustion power, cars from Max Verstappen’s Red Bull to Lewis Hamilton’s Ferrari crawled or stopped on track, the start was red-flagged, and the race began 93 minutes late after a 20-minute emergency patch.
Key Takeaways
- The bug lived in the standard software that every team and engine manufacturer must run, written by the FIA with ECU supplier Motion Applied and the teams, so it was not one manufacturer’s fault.
- It was triggered by F1’s wet-weather power mode, which limits MGU-K deployment from 350kW to 250kW in designated sectors and had never been used in a race before Sepang because 2026 had seen no official wet running.
- At Safety Car pace through the Turn 9 sector, boost pressure and engine speed dropped so low that a 60-second anti-cheating lockdown engaged and disabled the throttle on affected cars.
- The FIA’s fix was to remove the 250kW limit in the affected sectors through a software update loaded into all 22 cars in the pit lane in about 20 minutes.
- FIA single-seater director Nikolas Tombazis apologised, admitted the software “wasn’t tested in those specific conditions”, and promised a full review with teams and power unit manufacturers.
The incident happened at the relocated Bahrain Grand Prix, run at the Sepang International Circuit near Kuala Lumpur after the April races in Bahrain and Saudi Arabia were cancelled because of the Iran war. Sepang is famous for its afternoon thunderstorms, and one arrived about an hour before the scheduled 15:00 start, flooding the track and forcing a 40-minute delay before the cars were sent out behind the Safety Car. What followed was the first time the 2026 generation of hybrid power units had been run in genuine wet conditions at a Grand Prix, and it exposed a line of code nobody had seen fail. The race itself, won by Verstappen from Kimi Antonelli, is covered in our full Bahrain Grand Prix in Malaysia recap.
What happened on the formation lap at Sepang?
At 15:40 local time the field left the grid behind the Safety Car for what was meant to be a couple of exploratory laps in heavy spray. Within a lap, cars began slowing for no visible reason. Verstappen, at the head of the queue, radioed Red Bull: “I can’t accelerate! It’s not working, guys.” Hamilton’s Ferrari came to a halt on the main straight before he managed to restart it, Esteban Ocon and Valtteri Bottas also stopped on track, Liam Lawson and Gabriel Bortoleto reported the same loss of drive, and Isack Hadjar spun into the gravel at the exit of Turn 2. Because some cars were stuck and others were not, the field concertinaed into a mess: Verstappen ended up lapping the entire grid, and Antonelli described being “five-wide on the straight because we couldn’t understand what was going on”. Race control red-flagged the start and ordered every car back to the pit lane.
| Time (local) | Event |
|---|---|
| About 14:00 | Tropical storm floods the circuit an hour before the start |
| 15:00 | Scheduled start delayed 40 minutes to clear standing water |
| 15:40 | Formation laps begin behind the Safety Car; cars lose power |
| Shortly after | Start procedure suspended, red flag, cars return to the pit lane |
| Next 50 minutes | FIA diagnoses the bug and writes a patch; about 20 minutes to install in every car |
| 16:33 | Race begins behind the Safety Car, 93 minutes late; standing start on lap 3 |
Not every car was affected. The FIA said the fault caused “an unintended loss of power for a number of cars”, and reports from the pit lane identified Hamilton’s Ferrari, both Haas cars, both Cadillacs, both Audis, an Alpine and a Racing Bull among those that stopped or crawled, alongside Verstappen’s Red Bull Ford. The Mercedes works cars appeared to run through the formation lap without trouble, which helps explain why Antonelli and George Russell were among those left waiting for the rest of the field.
What is Formula 1’s wet-weather power mode?
The 2026 power units split their output almost evenly between the combustion engine and the MGU-K, the electric motor that recovers energy under braking and deploys it on acceleration. In the dry, the MGU-K can deliver up to 350kW. The regulations also include a mandatory wet-weather mode that reduces maximum deployment to 250kW in specific sectors of each circuit, chosen by the FIA for safety, so that drivers are not suddenly given full electric torque on a corner exit with no grip. One of those designated sectors at Sepang is the long left-hander at Turn 9.
All of this runs on the standard electronic control unit and the standard software that every team is obliged to use. As the FIA put it, the software is “created and validated by the FIA in collaboration with the standard ECU supplier and the teams themselves”. When race control declared wet conditions at Sepang, every team loaded the wet-weather parameters for the first time in a 2026 race weekend. The code had been tested, but only in the dry and in simulation, because a season that began in March had still not produced a wet session with the cars running in anger.
Why did the software bug trigger?
The FIA’s own description was “an unprecedented combination of low engine speed, low-grip conditions, wet-weather energy management settings and the Sepang circuit’s sector configuration”. In plain terms, four things lined up at once. First, the cars were crawling behind the Safety Car far more slowly than the software had ever been run, so engine speed and turbo boost pressure fell to levels the wet-weather mode did not anticipate. Second, the 250kW cap was active. Third, in the Turn 9 sector the system does not require the MGU-K to ramp down gradually, so electrical power could switch off almost instantly. Fourth, with so little grip, drivers were barely touching the throttle.
That combination looked, to the software, exactly like a team deliberately shutting down its MGU-K, which the rules forbid. The standard software contains a failsafe for that scenario, described by The Race as a “continuous offset” lockdown, which freezes the power unit for 60 seconds. At Sepang it engaged by mistake and, because the lockdown disables combustion power as well as electrical, it effectively deactivated the throttle pedal. Oliver Bearman summed up the drivers’ surprise afterwards: “I didn’t even know the FIA could control our throttle pedal.” Tombazis was candid about why nobody had seen it coming: “What caught us out was the fact that cars went at that very, very low speed, which was not normally contemplated.”
How did the FIA fix it?
Once the cars were back in the pit lane, the FIA’s technical department identified the trigger and wrote a software update that removed the 250kW energy limit in the affected sectors, so that the MGU-K could keep delivering power during very slow running and the lockdown would not engage. The update was distributed to all teams and, in Tombazis’s words, took “about 20 minutes” to install across the grid. Verstappen explained the delay from the cockpit side: “It was because they had to update the software, and then you have to load it into the car.” The race finally began behind the Safety Car at 16:33, with race control reverting to the original grid order rather than the scrambled formation-lap positions, and a standing start at the beginning of lap 3. The patch held: there was no repeat during the race, and the distance was cut from 56 laps to 55 to fit the time lost.
What did the FIA say?
Tombazis fronted up after the race rather than hiding behind a statement. “We didn’t manage to test the software as extensively as we would have liked, because there’s been very little wet running this year, and there was a bit of a combination of circumstances which caused this bug to kick in,” he said. “The software was tested, it just wasn’t tested in those specific conditions. If we had had a bit more testing, we probably would have managed to catch it in time.” He acknowledged the fans’ frustration: “It may have felt like five hours for spectators waiting for a race and for everybody else, which is understandable, and we are sorry about that, but I think it was quite a fast reaction given the problem.” He added that “sometimes things fall through the net and people learn, and you do a better job next time”, and confirmed a full review with the teams and the power unit manufacturers.
What did the drivers say about the Sepang software bug?
The paddock split between humour and anger. Hamilton called it “the Lego race” after having to restart his Ferrari on the straight. Oscar Piastri said: “I’ve never seen an F1 race delayed by a bug, that was a new one.” Sergio Perez, whose Cadillac was among those that stopped, said it felt like rental karting and that “what happened today is totally unacceptable”. George Russell admitted “I’d have been a bit disappointed if I was in the stands” and warned that “the more complicated you make things, the more there is to go wrong”. Lando Norris said the episode “just proves that we shouldn’t have any of that stuff on the electronic side”.
Verstappen, who went on to win, was the most pointed. “These engines are so complicated and a lot of software is implemented. When there is some kind of error or glitch, that’s the problem,” he said. “It was just like driving at 35 km/h going uphill, actually losing speed.” Carlos Sainz, a critic of the 2026 rules all season, went further: “F1 needs to have a hard look at themselves and see how we ended up in this situation. If it was a V8 aspirated, it would have never happened.”
Is the software bug a sign the 2026 rules are too complicated?
That is the debate Sepang reopened. The 2026 regulations hand the FIA far more real-time control over the power unit than before: sector-based deployment limits, overtake and straight modes, energy-recovery caps and now a wet-weather mode, all policed by standard software rather than by the teams’ own code. Supporters argue that is the only way to keep a 350kW hybrid safe and fair in the rain. Critics, including Sky Sports commentator David Croft, say the governing body simply did not do the work: “This falls on the FIA. You weren’t on top of things when it came to that race, and it was a farce.” Several drivers pointed out that the problem had nothing to do with the engines’ performance and everything to do with a rule layer stacked on top of them.
The timing is awkward for the sport. The FIA has already floated a return to V8 engines for 2030, and Sepang gave the drivers lobbying for simpler, lighter cars a ready-made example to point at. In fairness to the engineers, the bug was caught and patched inside an hour, and the race that followed was one of the best of the year. The lesson most observers drew was narrower than “scrap the hybrids”: F1 needs to run its wet-weather software in real wet conditions, at real Safety Car speeds, before it is used in a Grand Prix.
What happens next?
The FIA’s review with the teams and manufacturers is expected to produce a permanent revision of the wet-weather parameters so that the lockdown cannot be triggered by low-speed running, with the sector-based 250kW limits re-validated for every circuit. The first test could come quickly: the Singapore Grand Prix on October 9-11 is a night race in the tropics with a sprint on Saturday, and evening thunderstorms are common. If it rains at Marina Bay, every team will be loading wet-weather software that has now been patched but still not proven over a full wet race distance.
Frequently Asked Questions
What was the F1 software bug at Sepang?
A fault in the FIA’s standard power unit software that engaged a 60-second emergency lockdown on several cars during the wet formation lap for the 2026 Bahrain Grand Prix in Malaysia. The lockdown disabled both electric and combustion power, so the cars could not accelerate.
Why did the F1 cars lose power on the formation lap?
The wet-weather mode, which caps MGU-K deployment at 250kW in designated sectors, combined with very low engine speeds behind the Safety Car, low grip and the Turn 9 sector configuration at Sepang. The software mistook that for a deliberate MGU-K shutdown and triggered its anti-cheating failsafe.
How long was the Bahrain Grand Prix in Malaysia delayed?
The race started at 16:33 local time, 93 minutes after the scheduled 15:00 start. Heavy rain accounted for the first 40 minutes and the software bug, red flag and patch for the rest.
How did the FIA fix the software bug?
The FIA removed the 250kW energy limit in the affected sectors through an updated software release that was loaded into every car in the pit lane in about 20 minutes. The race then ran without a repeat of the problem.
Who won the race after the delay?
Max Verstappen won from pole for Red Bull, beating Kimi Antonelli by 2.307 seconds, with Lewis Hamilton third after recovering from 18th. It was the first win for the Red Bull Ford Powertrains engine.
