Reading OBD 2 trouble codes using nothing more than a check-engine light as your guide was normally done on older vehicles made in the 1970s, 1980s, and some vehicles made in the early 1990s before the onboard diagnostic system (OBD) became popular. Engine codes trigger the "check-engine" light and warn you that there is a serious problem with one or more of the sensors, valves or solenoids on your vehicle. If your vehicle's engine code can be read under the OBD 2 system using just the check-engine light, however, you can use the ignition key method to read the codes.
Insert the key into the ignition.
Turn the ignition key to the on position and then to the off position rapidly. Normally, an exact sequence of "on-off-on-off-on" must be performed within five seconds. This will cause the "check-engine" light to blink.
Count the number of times the check-engine light blinks. There will be two sets of blinking. For example, if the check engine blinks twice, this indicates "2." There will be a pause, and then the second set will start. For example, if the second set blinks three times, this indicates "3." The proper way to read this trouble code would be "23." The "23" refers to the numbered code in your vehicle's service manual.
