Is there any book/web site where i can learn more about the OBD System, and what are the correct parameters suppose to be ?
I'm interested in learning about 96-present Stock OBD systems.. And What i mean buy correct parameters is, lets say i look at the fuel trims . Whats normal and whats not for a correct running car/truck .Could you be a little more specific? LT1, Gen3, Gen4? Tons of tuning help out there for the Gen 3 computers, books, videos, classes. What do you mean correct parameters?
Thanks for explaining that a little more. I'm just trying to learn more on the how the system works . I don't have a problem with any of my car/trucks , but i have worked on a few with check engine lights on . I was able to correct most of them, just wasn't sure if they were running 100% ...On fuel trims, you have long and short term, short term are immediate changes and the long term adjusts to keep the short term close to 0%
lets say short term goes -11%, and stays there for a few moments, long term will begin decreasing to keep short term close to 0%. Generally anything between +9% and -9% long term indicates a "healthy" engine. Whenever outside of this percentage look for problems. Also, the phrase long term is a little deciving as it can change very quickly.
Whats the vehicle doing exactly?