When dealing with car troubles, a visit to the OBDII port under your steering wheel can clear up a lot of confusion really quickly. Unfortunately, we can’t just look at the port and tell what’s wrong, so we have to use a tool to read it. These tools come in two varieties: scan tools and OEM tools.
Most people use a scan tool. Scan tools are readily available, and significantly less expensive than OEM tools. A scan tool is a reader with a screen that displays emissions related error codes from the vehicle’s computer. They can tell you whether your check engine light means that your air intake valve is broken or if your knock sensor is getting low electric current. They can read any J1979 codes from any make and model of vehicle, J1979 codes having been standardized with OBDII. Scan tools are available at just about any auto parts store and are usually less than a couple of hundred dollars.
OEM tools, on the other hand, are able to not only read error codes from vehicles; they can interact with the vehicle. These tools only work on the specific brand of vehicle that they were designed for. They are not as widely available due to their prohibitively high cost of tens or even hundreds of thousands of dollars.
Why on Earth would they cost so much? There are several reasons. First and most obviously, they are expensive to make. Secondly, the high price tends to make it only cost effective for the dealerships to own them, concentrating much of the repair service. Third, and most importantly, due to the range of things that this system is capable of, including unlocking doors, rolling down windows and changing the timing of the spark plugs, widespread availability is a bit risky and requires training to prevent vehicle mishaps.
Widespread availability would also be a major liability issue. If people were customizing their cars at that level, they could overload the system and cause a catastrophe, similar to when you run a lot of programs at once on your computer and it runs slowly. Hitting the brakes is not something that can wait for on board computer processing. Mechanics at shops that do have these OEM tools are highly trained, and every product that can control the vehicle through the OBDII port is tested extensively.