Bahrain GP: Kevin Magnussen forced to start from pit lane
Renault's Danish rookie failed to stop for weighing during the second practice session when signalled to do so.
"The driver failed to stop for weighing during P2 (second practice) when signaled to do so by the red traffic light, the car was not returned to the FIA garage and work was undertaken," stewards said in a statement.
The Dane had followed Red Bull's Daniil Kvyat into the pitlane and there was some confusion over which car was meant to stop and be weighed. The Russian stopped, wrongly, while Magnussen continued.
He had been 16th fastest in practice at the Sakhir circuit for the second race of the season.