Toyota leads the Le Mans 24 Hours race heading into Sunday but ex-Formula One champ Fernando Alonso's hopes of winning at the first attempt took a knock when Swiss team mate Sebastien Buemi collected a one minute stop-go penalty that left him a lap down.
The sanction for speeding in a slow zone left them in second place, trailing their sister car by more than two minutes with 14 hours to go.
Alonso, the double Formula One world champion and Monaco Grand Prix winner who is chasing the 'Triple Crown of Motorsport', shares his car with former F1 drivers Buemi and Japan's Kazuki Nakajima.
Britain's Mike Conway is in front, driving the sister car with Japan's Kamui Kobayashi and Argentina's Jose Maria Lopez.
Alonso made his race debut with a feisty two hour and 43 minute stint.
It was Kobayashi, however, who led as the race reached the quarter distance and the light began to fade.
There was a scare on the opening lap when Andre Lotterer made contact with the rear of Buemi's car in the number one Rebellion.
Toyota changed the rear bodywork at the first pit stop before making another modification after Alonso's shift.
Jenson Button, the 2009 Formula One world champion, suffered debut disappointment when his Russian-backed SMP Racing car suffered an engine sensor failure and dropped to last place.
"You're never going to get anywhere near clawing that back," the 38-year-old said before finally getting out on track.
"Even catching the back of the LMP2 field at the end of the race is tough. It's become more of a test for us now."
Another former F1 racer in Colombia's Juan Pablo Montoya is competing in the LMP2 class but went off at the Indianapolis corner with the United Autosports entry dropping to 18th.
"I made a mistake and I ran wide at Indianapolis, just understeered off," he said.
"I just got on the brakes and locked them up and ran out of talent."
Spanish tennis great Rafael Nadal got the 86th edition of the race started, giving drivers the traditional instruction to start their engines.