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Q: check engine light

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my check engine light was on i took it to the shop, i was told the catalac converter needs to be replaced. over the last few days the light is off. since the light is off does that mean they could be wrong? do i still need to make this replacement. im not trying to spend the money if its not necessary

My car has 19300 miles.
My car has an automatic transmission.

Be sure the bulb for the check engine light has not simply burned out. To determine this, turn the key to the "on" position. If the check engine light briefly illuminates and then goes out (the light will normally illuminate briefly while the PCM runs a self diagnostic) then the bulb is good. That would mean you do have a circumstance where the "trouble" has gone away, even if temporarily. It is possible for the check engine light to go out on its own when the underlying trouble was transient and that will happen with certain codes pertaining to "catalytic converter efficiency", for example Code P0420. As far as what to do at the moment, if the check engine light is not on, you need do nothing because there is no fault at the moment. But, to answer your question about misdiagnosis and what the future may portend, as well as how to handle future instances of this, we would need to know the Diagnostic Trouble Code that your car was reporting. With that code, we can give you a much better idea of the range of possibilities, what to look for, and what to expect.

If the check engine light comes on again, consider requesting a check engine light diagnostic. During such a diagnostic, a certified mechanic from YourMechanic would use a code scanner to retrieve the specific diagnostic trouble code(s) from your car’s PCM that have caused the check engine light to illuminate. Using those codes, the appropriate individual vehicle components or sub-systems (often a sensor, circuit, and the like) are tested to pinpoint the cause of the fault or the reason why the check engine light has illuminated. Once the faulty part or component is identified, it is explained to your satisfaction and the mechanic will let you know of the cost to repair. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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