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A few months ago, my check engine light popped on, and started spitting a 420 code, and later a 430 code. According to my scanner, it means something might be up with the left and right bank catalytic converters.
I haven't noticed any actual change in the vehicle's performance, engine behavior, or gas mileage. The 430 code in particular will briefly resolve itself after a few straight hours of highway driving.

Went to my local Pepboys for an oil change and asked about it, but they just ran a scanner again and the guy gave me a vague estimate of $2000 or more to replace "the whole thing." So I just left, and after doing some research on my own afterwards, I'm a little suspicious.

I'm gonna try and take it to a independent shop I actually trust later this month to get a proper diagnosis, but the problem is I don't know much about the exhaust system. I just want to make sure it passes the Pennsylvania inspection this spring without totally destroying my bank account, because two grand seems really excessive.

Is there anything else I should check/fix or get checked/fixed before just trying to replace the cat(s)?

Am I playing with fire if I ask to use something other than an OEM replacement? I don't live in CA or NY, and I see fed-compliant systems from Magnaflow for example that are literally half the price of what MOPAR charges on their website.



(Apologies in advance if this was already dealt with in another thread. I did try searching the forums, but didn't see anything really exhaustive.)
 

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A few months ago, my check engine light popped on, and started spitting a 420 code, and later a 430 code. According to my scanner, it means something might be up with the left and right bank catalytic converters.
I haven't noticed any actual change in the vehicle's performance, engine behavior, or gas mileage. The 430 code in particular will briefly resolve itself after a few straight hours of highway driving.

Went to my local Pepboys for an oil change and asked about it, but they just ran a scanner again and the guy gave me a vague estimate of $2000 or more to replace "the whole thing." So I just left, and after doing some research on my own afterwards, I'm a little suspicious.

I'm gonna try and take it to a independent shop I actually trust later this month to get a proper diagnosis, but the problem is I don't know much about the exhaust system. I just want to make sure it passes the Pennsylvania inspection this spring without totally destroying my bank account, because two grand seems really excessive.

Is there anything else I should check/fix or get checked/fixed before just trying to replace the cat(s)?

Am I playing with fire if I ask to use something other than an OEM replacement? I don't live in CA or NY, and I see fed-compliant systems from Magnaflow for example that are literally half the price of what MOPAR charges on their website.



(Apologies in advance if this was already dealt with in another thread. I did try searching the forums, but didn't see anything really exhaustive.)
@Toastyy; This might help give you a little more insight; I see bad O2 sensors mentioned a few times;

Jeep Grand Cherokee WJ - Diagnostic Trouble Codes

P0420 Catalyst System Efficiency Below Threshold (Bank 1) Catalyst 1/1 efficiency below required level.

P0430 Catalyst System Efficiency Below Threshold (Bank 2)

https://www.obd-codes.com/p0420

https://www.obd-codes.com/p0430
 

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Discussion Starter #3
Well, I finally got it in at a shop I trust, and they did a proper diagnosis. It's definitely the cats going bad, not the sensors. Luckily, they gave me a pretty fair quote for replacing everything, and actually gave me the number of an exhaust shop out in the boonies where swapping out cats is pretty much all they do, and they have really low labor costs.

They also confirmed that it's nothing to really worry about until inspection time.
 
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