Before I take it to the shop I have to stop here and ask the real experts that don't charge you for sound advice. My service engine light came on. It is a full size 2003 model that just went over 40k miles. I have maintained the vehicle as much as humanly possible getting all the oil changes done and services per the owners manual. I would like to know if the service engine light automatically comes on at 40k miles to force the owner to the shop for service or could this be something else that should get checked out? The only things I have done different with the truck lately is put in a bottle of fuel additive in it at 40k miles and I have been running the vehicle faster that normal. I normally drive it for 25 miles in the early morning at about 75 mph but I have recently gone as fast as 90 mph on several occasions. Finally after the light came on and during my next fueling I noticed that the fuel cap was not turned all the way tight. Since then I have put another tank full in it and the light is still on. If it's just an automatic light that comes on at 40k then I would like to know how to reset it. Thanks in advance.
Diego