Fernando Alonso says he retired from the Italian Grand Prix to protect his Honda engine after suffering a loss of power on lap 46.
Alonso was dicing with team-mate Jenson Button for 14th when he pitted after feeling a loss of power in his car. A switch change as the Spaniard drove through the pit lane temporarily solved the problem, but it returned at the end of the lap and forced him to retire.
"I got a good start today, then a couple of cars made contact at the first corner, which slowed me down," Alonso said. "Then, at the second chicane, I came close to Jenson and eventually lost all the advantage I'd gained. "Jenson and I were on two different tyre strategies, to try to cover all possible opportunities. I was on the Prime, which was one second slower than the Option, so I had a slower first stint, but then I was a bit quicker in the second.
"In the final laps, I felt a loss of power and was told to retire the car, so as not to cause further damage. We were outside the points anyway, so it was a wise decision."
The Italian Grand Prix weekend has given the first genuine signs of cracks forming in the relationship between McLaren and Honda, with the team's package still a long way off the pace.
Honda chief Yasuhisa Arai said: "Fernando's car unfortunately had an electrical control board issue, and therefore had to retire. We will need to investigate the reason for this further, but we do not believe there has been any effect on the ERS itself."