Meineke Car Care Meineke told me i needed a $600 convertor system and it was just an 02 sensor but still had to pay??? Houston Texas

I am a former Operations Manager for Meineke car Care Centers & a former owner of a Meineke store. I, from the repair side, have experienced this problem numerous times concerning emission systems. Although a blinking light means there is a "hard code" available, it can be that there are more than one, but unless the first one is corrected, the remaining codes are hidden.
In almost 100% of the instances where an O2 sensor was diagnosed as being faulty, it was found that the converter was the culprit, hence, cause & effect. A partially restricted converter will overheat the sensor causing it to fail. Diagnosing emission failures is extremely difficult, even for dealerships. That is the reason many dealers recommend converters, sensors, etc. as a "package", no matter what the diagnostic codes show.

I have always taught technicians, owners & managers to inform customers that the first repair may not correct the entire problem. The first diagnosis is just the first step in possibly a string of other repairs.
I cannot begin to tell you how many times a customer has been in my store complaining of an engine light on and when questioned about how long it had been on, the answer was a year or two. In other words, the only reason they were in the shop at all is their vehicle was rejected for state inspection. If they had repaired the vehicle when the light first came on, possibly nothing but a converter or sensor would have been all that was necessary.

Knowing that this customer was a used car dealer says a lot in itself. It's possible the original owner of the vehicle traded it in BECAUSE of the warning light.