Is a check engine light a simple matter of plugging in a device and reading the code and buying a part? Infomercials and some parts stores would like you to think so.
Retrieving the code from your On Board Diagnostic (OBD) port is relatively simple but don’t be fooled into thinking it will give you the whole problem. It simply outputs a manufacture’s code that is set because perimeters have not been met in a self-test. It does not, necessarily, say that a particular part is bad. The part could be bad or there could be other conditions causing the sensor to read outside of its limits.
Oxygen sensors are great examples of this. You could have a code saying that a sensor is reading out of range. An uninformed decision will cause one to spend hundreds of dollars to buy the sensor and it not cure the problem. A leaky fuel injector could be causing the engine to be rich—a condition of to much fuel for the oxygen in the cylinder. Further troubleshooting should be used or a simple changing the place where you buy fuel has worked in some cases.
A scan tool that reads code is a great tool, but it is just that a tool. It provides you with a starting place. It should never be the substitute for troubleshooting. You should be leery of any mechanic that simply says a sensor needs to be replaced solely based on the code present. Though it could be that simple if it is not you begin the game of standing back and throwing parts at your car to fix it—expensive parts.
If you dare to dive into working on your own car to save money it is best to purchase one that not only reads codes but can stream information from the computer, such as the innova 3140, it is relatively cheap and using it is simple.
You would also want to buy a great service manual. The digital version from ALLDATA DIY gives you great troubleshooting helps and info as well as service procedures.
Working on your own vehicle is extremely intimating but with patience and some upfront money you can save money or at least make informed decisions.
So next time you are awake at night and the infomercials are selling some sort of car doctor device remember that it is just a tool that provides a starting off point it is not a fix.