[high&dry]

Daughter took her car for an oil change and courtesy check. They found 3 codes one which I cleared P0328 by replacing and relocating the knock sensor the other 2 I read is either a catalyst converter for bank 1 and 2 or CO2 sensors. This vehicle has 4 CATs, pre and post so I assume the codes are picked up from the pre cat which also has CO2 sensors before and after. Would this be a correct assumption? I was looking at the Walker brand CATs which I understand fit in with no issues.

 

[dejablue]

How many miles??

 

[high&dry]

167728 miles. Someone mentioned trying sea foam not sure that will work.

 

[dejablue]

That not going to fix this kind of problem.
What kind of gas are you using low or high ot ??

 

[high&dry]

Low Oct

 

[dejablue]

Its probable the cats .
Has she had any problem before this.

 

[high&dry]

No. May need to have a muffler shop check the cats to be sure.

 

[dejablue]

Are there any cracks on the ex-manifold??

 

[high&dry]

None that I can see or hear.

 

[high&dry]

One thing I can't figure out is how both sides report cat failures at the same time when both are separate from each other. I would tend to believe problem is upstream involving a bad combustion mix or sensor related.

 

[clunker]

I have the exact same 3 codes, but I only have 130k miles. The previous owner had the knock sensor replaced, but I have learned that this was probably not necessary. Based on my online research, the knock sensor does not throw a code when it has gone bad. It throws the code when the engine is pinging (or at least the sensor thinks it is). If you get the P328 code, it means something else is wrong.

The other two codes are what I am more concerned about. I also have it reporting both banks. As you suggested, I am thinking the problem is upstream. Research suggests that a rich fuel mixture could be to blame. How is your gas mileage? A stuck fuel pressure regulator could be the problem, or some source of incomplete combustion (plugs, wires, etc.). You got more responses to your post than I did, so I will adopt your thread and give feedback if I learn anything new.