Catalytic converter issue

[Markus Escamilla]

So i have a p0430 and I don't really want to buy 2 new cats. Would it be a good idea to just get both cats removed and put a pipe in place? Or should i just spend the money and get 2 new cats.(my truck is 98 Cheyenne with a 5.7) 

[CamGTP]

If you want the light to go away you'd need to put new cats in there or have the computer tuned to turn off the check engine light codes.

 

If you go with an aftermarket cat, don't find the cheapest one on the market as they won't last.

 

I've actually had good luck with Walker replacement weld in cats. I've used two of them on two different vehicles and they lasted several years without ever tossing a code. I don't recall the price at the moment but they were around $100 I think, maybe less.

[Black02Silverado]

What mileage is on that beast?  Does it burn any oil?  Just curious as to why the CAT's need to be replaced.  If you don't fix the problem, if there is one, you will just be doing all over again.  Reason being is I know of several vehicles well over 300k and have the original CATS. 

[Markus Escamilla]

5 hours ago, Black02Silverado said:

What mileage is on that beast?  Does it burn any oil?  Just curious as to why the CAT's need to be replaced.  If you don't fix the problem, if there is one, you will just be doing all over again.  Reason being is I know of several vehicles well over 300k and have the original CATS. 

240,000 miles...it isn't really burning a noticeable amount  of oil...but sometimes the exhaust stinks only on one pipe. On another post someone had said that the smell is mostly definitely a cat and not an 02 sensor

[Brian Lindsey]

i would get oil problem fixed first , then replace cats , you engine computer adjust engine performance based on upstream and downstream oxygen sensors readings

 

[davester]

It's my understanding that only the upstream sensors are used for controlling the engine, and the downstream sensors are solely for tracking how well the cat's are working.

[Tom_1991]

On 2/26/2020 at 5:40 PM, davester said:

It's my understanding that only the upstream sensors are used for controlling the engine, and the downstream sensors are solely for tracking how well the cat's are working.

In my understanding (OBD-II), some vehicles use both up and down stream sensor to control fuel trim, some use upstream only.

The way to tell is look at Live Data via OBD scanner, if STFT (Short Term Fuel Trim) of sensor 2 (STFT B1S2 or STFT B2S2) reads 99.x%, that means the vehicle only use upstream sensor to control fuel trim. STFT=99.x% means this the data form sensor don't contribute to fuel trim control, as you say, only used to tracking how well the cat's are working.

If it's data acts similar with sensor 1 (STFT B1S1 or STFT B2S1), up and down around 0%, that means the vehicle use both sensor to control fuel trim.