Webber, who battled with Button for more than half the race in Valencia, could finish only ninth as the Red Bulls struggled to find any pace on the stop-start street circuit and is now 20.5 points behind Button.
"Additionally, a malfunctioning stop lamp switch may also result in intermittent operation of the push-button start feature, affect the operation of the brake-transmission shift interlock feature, preventing the shifter from being moved out of the park position and cause the Electronic Stability Control (ESC) malfunction light to illuminate, " stated NHTSA documents.