The contact owns a 2021 Honda Pilot. The contact stated that after idling at a red light, the Auto Start failed to operate as designed. The contact had to shift to park(P), and several attempts were needed to restart the vehicle before the contact was able to continue driving. There were no warning lights illuminated. The vehicle was taken to the dealer, who diagnosed that the battery had failed and needed to be replaced. The battery was replaced; however, the failure persisted. The vehicle was not taken to the dealer to be diagnosed or repaired. The manufacturer was not informed of the failure. The failure mileage was approximately 33,000.