We’ve all seen them and some have had them show up in the dash board of our cars, the dreaded Check engine light. While not the end of the world they can be a costly problem for some people.
With that in mind, it is important to be accurate with the diagnosis because replacing the wrong parts will cost even more and you will still have the same problem.
A seemingly popular option is to go to the local auto parts store, Autozone, O’reilley etc to have them scan the codes and guess at a repair and supply the parts. Notice I said guess, that is because it basically is that, a guess. Check engine light diagnosis is not something that is guessed at with any certainty.
How do you diagnose a check engine light?
We often compare a check engine light diagnosis to a medical doctors diagnosis. The reason we do this is because we can get a better idea of what’s needed to diagnose a check engine in comparison to us going to the doctor, it seems easier to understand. For example, if we don’t feel good and we go to the doctor, he will begin the “diagnosis” process with questions about how we feel etc. Then may use testing to help determine the cause and could even look up a possible prognosis. Diagnosing a check engine light is similar to that, we ask questions on the symptoms, if there are any, we will run tests and utilize repair information to perform a diagnosis of the problem. Seems easy enough, but it’s not always that easy. Most automotive components have testing procedures to find fault in a part, which the manufacturers create for the technicians to use to diagnose a problem. Some of these repair procedures can have over 20 different steps!
Isn't there a machine that tells you whatever is wrong?
There is no machine in the world that can print out what part to replace. That’s right, there has never been such a machine. What we see when we hook up the scanners is a code or codes. That is where the diagnosis begins, with that code we then look up the diagnosis procedure to determine where the fault it.
What the Autozone’s and O’Reilleys are doing is a guess at what could be wrong as they have no ASE certified technicians diagnosing the problem.
Trust me, we too wish there was a machine that would tell us all the problems with the cars, it would save so much time and money. The technology simply does not exist or is too expensive to be able to build a car and machine to diagnose its own problems.