what i wanna know is if a service engine light can erase by itself if stuff has been fixed or otherwise corrected. the car am talking about is a 2000 mustang GT that just got a saleen M91 supercharger installed, saleen ecu and bbk fuel pump. we found a vacuum leak but it was fixed, the car was running fine after that but the service engine light was still on, but yesterday somehow the light just turned off so am wondering if it can turn off by itself.(the car is making 350rwhp & 377rwtq with the supercharger, off-road x-pipes and flowmasters and a 75mm throttle body i might have to change the tranny sometime soon ).