Use a car code reader by plugging the device into the diagnostic link connector of the vehicle with the engine off. The connector is generally located under the dash. After plugging in the car code reader, turn the vehicle on and follow the device's instructions to receive trouble codes.
Any issues with the vehicle pop up on the car code reader device as a set of numbers. Higher-end car code readers also display in words what the trouble code signifies. For example, the trouble code number may indicate that the vehicle's oxygen sensor is lean.
Some less expensive models only display the numeric trouble code, as of 2015. If the card code reader only shows numbers, the user should look up the code in a reference book. The manufacturer of the car code reader may also list the trouble codes on their website.
Vehicle owners can make the appropriate repairs after determining the trouble code and vehicle issue. Owners that do not know how to fix the issue can refer to a vehicle repair manual for guidance. Other resources for repair information include online shop manuals and vehicle repair Internet forums. If the vehicle owner is unable to repair the issue, a certified auto mechanic should repair the vehicle.