The Electronic Control Unit (ECU) in a car provides information on current problems that the car may be experiencing, as well as issues that could become problems in the future. The OBD2 reader downloads this information in the form of codes and then translates these codes into a format that the owner or mechanic can understand. There are many types of personal OBD2 readers available for purchase, ranging from basic to advanced.
Determine the type of OBD2 personal reader you need. Some readers can stand on their own while others require additional equipment, like a laptop computer. Handheld readers are simple to operate and transport while PC-based readers have unlimited storage capacity and higher-resolution screens (see Resources below).
Look for a reader that can read both generic codes and manufacturer-specific codes. Generic codes are those that are required by law and they range from P0100 to P1000. Manufacturer-specific codes are those created by manufacturers for specific cars and these codes are all higher than P1000.
Purchase a reader made specifically for the type of car you drive. For instance, if you drive a Volkswagen or Audi, you may benefit most from a code reader created specifically to identify problems that are unique to these cars.
Select a personal reader that can clear as well as read the Diagnostic Trouble Codes (DTCs). Such readers are able to erase all the codes that appear, as well as turn off the "Check Engine" light.
Select an OBD2 personal reader that can support all protocols. The standard protocols include SAE J1850 PWM, SAE J1850 VPW, ISO 9141-2, ISO 14230 KWP2000 and ISO 15765 CAN. The pins that are available on the 16-pin female port in your car indicate which of these protocols is compatible with the computer in the car.
Select a reader that can display codes in more than one language. If you are multi-lingual, or you travel frequently to other countries, a reader with such a feature may be important to you.
