DETRIOT — Within a month of OnStar launching its monthly e-mail vehicle diagnostic service, enrollment has surpassed 100,000 customers, according to Telematics Update magazine. OnStar Vehicle Diagnostics automatically performs hundreds of diagnostic checks on four key GM vehicle operating systems — the engine/transmission, anti-lock brakes, airbag, and OnStar. The vehicle is automatically programmed to send the results via e-mail to the owner each month. The e-mail report also provides maintenance reminders based on the vehicle’s current odometer reading, remaining engine oil-life, and other relevant vehicle ownership and OnStar subscription information.