When you turn the key on sometimes the check engine light will stay on and sometimes not. If the light stays on the truck will start then stop immediately and will contiue that trend. If the check engine light does not come on the truck will run great. When the check engine light is on it offers a code for the MAP sensor (Code 34.) THe MAP was changed, but to no avail. A loose ground was found going to the computer but that did not change a thing. The whole system can be reset by using the "key" for reading the computer and starting the vehicle. When the "key" is in there is a buzzing sound engine caprtment.