Thats definately a helpful article. Thank you. My scan tool has freeze frame that shows fuel trim % at the point it was out of parameter... but whats allowable?? .It also shows vehicle speed to be zero all the time. Are they connected, if the pcm uses load % would it use speed also?? The light came on at idle. I'm guessing Mass Air problem. I wouldnt think O2's on both banks went bad literaly over night or at the sametime. Checked for vacuum leaks, cracked boots and hoses. Thanks again