I recently replaced the dual catalytic converters on our 1999 4runner with a single Magnaflow cat. from Autosound. How long should it take for the Check Engine Light to come on? From my understanding, the 4runner had the Calif. emissions, hence the dual cats. Replacing them with a single cat. should throw the CEL, but in the week since I had it done, the CEL has not come on yet. Any thoughts onthis??

 

It may never come on. As long as you have a cat on there at all it may stay off completely. The O2 sensor after the cat is just looking to verify that there one in place, I am not sure that it could distinguish between 1 or 2 converters.

 

I replaced the stock cat on my 2.7 with a carsound one. The CEL never went on in over 2 years since the headers. But it just recently came on during a road trip a few months ago. Sometimes it goes away on its own, but for the most part, I always have a CEL due to my non CA spec. cat.

I have a stock cat, but I havent welded a flange to the other side so I can install it yet.