It's raining out now, so I'm not going to go crawl under my truck and see, but typically there's a secondary O2 sensor on all OBD2 cars that just runs checks to make sure the cat is working within spec.

 

if your looking for a highflow cat I would go with a magnaflow highflow cat. thats what I have and I'm very happy with it. [sm=gears.gif]
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CARPAL TUNNEL SYNDROME ADVICE

 

Well I looked under mine and theres no sensor, just one before the CAI, thats why my cat is still on because of that sensor, I dont know how to get around it. And mine is the V6.

 

DakotaSport, i think you mights be getting certain components confused. a CAI is a cold air intake. you also should have two o2 sensors, unless the previous owner removed the second one. do you have a check engine light? the first o2 sensor will be located with 8"-16" before the catalytic converter. the second should be within the same distance, downstream of the catalytic converter. if you dont have one, then it has been removed. you should look into this further and see if the wiring had been spliced and had a resistor placed on the connection to stop a check engine light from being caused.

 

yeah, CAI = intake, CAT = exhaust

Totally different parts.

The rear O2 possibly could be sticking out of the top of the back end of the CAT so you might miss it. It is possible, like virused said, that somebody removed it and put a mechanical fix in to prevent the CEL from coming on due to the cat not working.

Searching the OEM parts online there's a rear O2 sensor w/12" pigtail for $106 MSRP for the 3.9.

 

.......man, a shop told me I had 1 Sensor.. I just looked under there and there I saw the second one on the other side..... So I do have TWO Sensors...Oh no! I have the stock cat sittin on my truck.... hmm i gotta replace that... and i'm still getting better MPG then averige people on reviews, cant wait till I get my headers in and high flow cat, it'll be so much better.

And, I read on here before and someone called a Cat a CAI, I thought it was weird but w/e... sorry for the confusion.

 

back to the muffler part of this thread... aero turbine is a free flow muffler that MAY keep some low end torque around to minimize low end loss (& mpg). I've ordered one for my truck and should be here tues of next week. I'm planning on putting it infront of the 30" straight thru magnaflow to hopefully bring back some low end torque lost during the mag install...

 

You lost torque with a free flowing exhaust? What size pipe did you use?