If your car doesn’t have an onboard computer, you’ll need to use a code reader in order to diagnose any potential problems. Code readers can be purchased at most auto parts stores and are relatively inexpensive. Once you have a code reader, simply hook it up to your car and follow the instructions that come with the device. Code readers will provide you with information about what fault codes have been detected, which can be helpful in diagnosing the issue. In some cases, you may be able to clear the codes using the code reader. However, if the problem persists, you’ll need to take your car to a mechanic for further diagnosis and repairs.