One of the most common problems on late model vehicles is the never ending yellow check engine lights that we’re all faced with.  And that leads a lot of drivers into some very expensive repairs, because there are a lot of mistakes that are made in finding the cause of these check engine lights.

The most typical thing that happens is that a scan tool is hooked up to the computer system in the vehicle. The scan tool gives a data stream and it gives codes. Now, these codes can spell trouble, because often the technician will look at the code and say that, well, you need whatever the part is that the code refers to. Well, that’s wrong. You see the code doesn’t tell you what is at fault under the hood of your car. It only tells you what is being affected by what’s wrong.

You see, the reality of it is you don’t start with a scan tool. You start with an engine analyzer and you do baseline testing of various things under the hood of the car, the plugs, the wires, the coils, all of these things, including vacuum hoses. They all have to be checked to make sure that they’re good. Then, after all of that is done, it goes on into the scanner. The technician reads the data stream, and the last thing is the codes. Now, once they have the codes and they’ve checked all of the other things, they do not replace the part that the code refers to. In reality, what they do is they go to a diagnostic tree that is relative to the code, and this diagnostic tree, it asks various questions and you answer it with a yes or a no through a test. And by going through the whole thing, it tells you what is wrong with the car. And that means that the check engine light is going to be repaired permanently.

If you have a question or a comment, write to me.  If I use your letter, I’ll send you a MotorWeek T-shirt.  The address is:  MotorWeek, Owings Mills, MD, 21117.