I have a 2000 4runner the cel has been coming on for 3 years indicating cat converter. I disconnect battery and thelight stays out for 400 miles sometimes and only for a few miles other times. It always passes inspection in Mass. if I go 100 miles or so with light out. To me this shows that the converter is working. My mechanic replaced a sensor butit did no good. Now he wants to replace the cat at a cost or $1,200. or more. Does anyone know if I can try anything else first. My inspection is due this month.