1
Plug the OBD-II scanner in to the Diagnostic Link Connector port together with the ignition off. This is a 16-pin plug around 2-inches lengthy by 3/4-inches high; on the 1999 VW Jetta, it truly is located underneath the dashboard close GM MDI to exactly where the driver's left knee could be. The plug itself is usually purple.
2
Turn on the ignition and start the engine. Since the vehicle battery powers the OBD, you are going to not be capable of read any codes with all the ignition off.
3
Read the code on the OBD-II scanner. It will be a letter--usually "P"--followed by four digits. You can go online and look up what the code signifies to be sure there is no mechanical problem.
4
Clear all codes using the OBD-II scanner. Once the machine connects to the vehicle's system and reads the trouble codes, it will give you the option to reset, or clear, the OBD. You should only do this if you are certain the problem is nonexistent or minor.
5
Unplug the OBD-II scanner and turn off your automobile Auto code scanners. Once cleared, the Check Engine light will remain off if the problem was nonexistent--for example, the light was just a service-check reminder. If the problem persists, the light will turn on again when the onboard system does its next routine check and rediscovers the issue. This can be anywhere from a few to 50 miles.
