Repairing modern vehicles can be expensive. Throw parts at a problem and hoping you guessed right isn't an option. You will usually run out of money before guesses. What is the right way to diagnose a running problem? Fix that check engine light? What kinds of tools are required to do a proper diagnosis? What kinds of test can be performed to determine the source of the engine performance issue? How do you go about properly diagnosing OBDII system failures? Whether you are a seasoned technician, a beginner or a Do It Yourselfer, the information contained in this book can help you make diagnosing OBDII driveability concerns easier. Guessing is no longer an option.