Since 1996, all cars in the United States have used the standardized On-Board Diagnostics Series-II system. OBD-II differs from all previous systems not only in its complexity and capability, but in the fact that the programming language has been standardized so that service personnel don't need to use a different computer system to diagnose each brand of car they work on. Clearing the codes from an OBD-II car like the Impala is a simple matter; just ensure that you fix the problem before clearing them so the check-engine light doesn't come back.
Locate the OBD-II diagnostic port under the dashboard, beneath your steering wheel. The OBD-II diagnostic port is a trapezoidal port that strongly resembles the port on the pack of your computer where the monitor plugs in. There is a black or orange plastic plug covering the port; remove it.
Turn your car key to the "On" position, but do not start the car. Plug your code scanner into the port and give it a moment to access the codes. After displaying the code, the scanner will give you the option to clear it. Select "Yes," unplug the scanner and replace the cover.
Clear the codes by resetting the computer. The alternative approach here is to reset the computer by depriving it of power.
Pop the hood, loosen the negative battery terminal and remove the terminal. Allow the car to sit for five minutes, then replace the terminal and tighten it. The only downside to this approach is that disconnecting the battery will clear the computer's entire stored memory, including your clock and radio settings.
