The FIA said an unprecedented combination of low engine speed, low-grip conditions, wet-weather energy management settings and the Sepang circuit's sector configuration led to an unintended loss of power for several cars. The issue had not been detected during testing or during the laps to the grid. During the race delay caused by heavy rain, the FIA technical department removed the energy limit constraint in the affected sectors through an updated software release distributed to all competitors, enabling teams to make necessary changes to the power unit before the race start.
Ferrari's seven-time world champion Lewis Hamilton described having to stop his car on track and restart it, saying it was a career first. Red Bull's four-time champion and eventual race winner Max Verstappen compared the experience to a 'Lego race' held at Silverstone before the British Grand Prix.
The episode is the latest in a difficult first season for the new era of cars and engines, with drivers unhappy since the opening race with the power units' increased electrical component and the need for energy management.
FIA single-seater director Nikolas Tombazis told reporters that a lack of preseason testing in wet conditions had contributed to the chaos. "Some cars went very slowly, almost came to a standstill. There was a bit of a concertina effect between cars, and some cars almost stopped completely," he said. "That bug prevented the power from being redeployed, and for the cars to start again. I think if we had had a bit more testing, we would probably have managed to catch it in time, and not have such a situation."
The FIA has said it will undertake a full review of the issue together with the teams and power unit manufacturers.