Edmunds Answers



  • karjunkie 02/17/09 7:28 am PST

    Diagnostic codes are standarized and most scanners can read the codes through a standarized port in post 1996 cars and trucks and tell you what they are. The scanners will visually display the code on their small screens. However, your dealer or mechanic may have much more powerful diagnostic computers that go into far more detail as the the condition of the engine and transmission. There is no way for the shop to turn the light off without correcting the problem. However, just because the code says change the sensor and you do, does not mean that this works 100% of the time. The reason is that you can get a "false" code being thrown by the engine computer or being generated by another defective part that causes the other part to malfunction. Many sensors are interdependent in order to run your engine efficiently.

  • gar_fanatic 03/02/09 11:47 am PST

    No, not all scanners are the same. They range from code readers (like what your part store has), to full blown scanners that list tons of information on your vehicle (like the current rpm, how much fuel it's using at that exact moment, historical graphs and data, what all the sensors data is, etc.) The more complex the machine, the more expensive it is. Then there are the scanners that only the dealers can get/afford, which have security information and computer programming information.

    All the codes are standardized. On the more advanced scanners, the code is displayed on the screen, with the description. Then the mechanic checks the sensors that the code is referring to to see if it's a malfunction of the sensor or a malfunction of something else. If the sensor is reading some information, then the problem is somewhere else. If the sensor looks "dead" then the sensor needs replaced. For example, if the code is for an oxygen sensor, then we can check the data coming out of that oxygen sensor. By reading this data, we can determine if the sensor is malfunctioning or the catalytic converter is bad.

    No, we can't just shut off the light without finding the reason it was on if there is truely a problem with the vehicle. The light will come right back on again after two trips, if there is a bad part.

    Source: work in an auto repair shop.


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