I keep getting a check engine light for cat below threshold. Muffle guy said I needed a new pre-cat that is made into the Y pipe. 1500 dollars at the dealer. I thought about gutting it and use a o2 sim to keep the check engine light off. Has anyone used them before. I found one that says to wire a 1 micro farad cap and a 1000000 resistor in parallel. The car is an 04 montero non sport. Thanks Chad

 

Welder, I understand your thinking but I'm wondering how your set-up is going to work with your vehicle's engine control system. If you gut your cat and then put in a "fake O2 sensor to fake out your check engine light, won't your ECU still wonder what the heck is going on down there send all kinds of wrong mixtures to your cylinders? Or do I have thing whole thing completely wrong?

I've never used one of these. BTW, are you out here in California by any chance?

New Cats + California = $$$$$$$

 

I am in TN. From what I have heard the rear o2 is just to make sure the cat is working. It doesn't adjust the fuel. Chad

 

OK, Chad, that makes sense. Good to know.

These reason I asked about where you were from is as you probably know California has this crazy bill they passed that all SMOG devices have to be from the original manufacturer or they won't pass the visual inspection. This of course can add hundreds of dollars to parts like catalytic converters, distributors, and pipes as well as oxygen sensors.

Consequently, I'm thinking that you should be able to find a cheaper Y pipe and cat than for what your dealer quoted you by searching your local CL or vehicle graveyard. What you quoted sounds like California prices.