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Aftermarket Catalytic Converters - AP Eastern


Topic starter

Hi everyone,

Alright, here's the low-down:

2005 Toyota Tacoma V6 Crew Cab with 4x4. 248,000 original kms (154,000 miles).

Vehicle shows codes P0430 and P0420, and I have had them check by the shop to confirm that both manifold converters will need replacement. I have already personally replaced all 4 oxygen sensors. There is also an exhaust leak at the Y-joint that will need to be dealt with as well.

The shop that I had this all diagnosed quoted me $2,100CAD for parts and $430CAD for labour, totalling $2600CAD-ish after tax.

RockAuto has AP Eastern converters that would be just over $1000CAD all-in (taxes and shipping included). However, they are listed under OE-Design, which I'm not sure if that is a huge deal or not. 

Alternatively, I could go to a muffler/exhaust specific shop and see what they would quote to perform the repairs.

I don't have to do emissions testing here in Canada, nor do I plan on moving to Colorado, New York or California where they would do EPA testing. My main goal here is to reduce engine wear and get my performance and mpg back to where I'd like it. I've also attached the particular parts I'd be looking to buy from RockAuto Does anyone here have experience with AP Eastern or other aftermarket converters? Does anyone have advice as to how to tackle this problem? 


Alright, I've found this forum discussing aftermarket Cats. Seems that Walker is top, AP Eastern is a close second.

Comment what you think, but I'll probably spring for AP Eastern to get a direct fit and to keep my costs under $1,000.00

8 Answers

Setting catalyst system efficiency codes on both cylinder banks (on different cats) at the same time? 

That seems like a big coincidence.

 OK, fair enough but it still seems suspect to me.

On top of that you have at least one known exhaust leak and it's downstream of both cats at the Y connector (closer to both downstream O2 sensors) and it isn't good practice to condemn cats over efficiency codes when you have known exhaust leaks. (exhaust leaks "pulse" O2)

Also, you mentioned that you're experiencing performance and fuel mpg declines.

The exhaust gasses (feed gasses) going into the catalytic converters have to be kept in a very narrow range to properly "light off" the cats so they can work efficiently. So what do your fuel trims look like?  

Also, did you replace those A/F and O2 sensors with OEM? Believe it or not it makes a difference. 

The bottom line is, unless your cats are causing a restriction (elevated back pressure) in the exhaust, replacing them won't help with performance or fuel mileage.  You can pull out an A/F sensor and stick an exhaust back pressure gauge into the hole to see if there's too much back pressure.

If there's too much back pressure at the A/F sensor but not at the downstream O2 sensor then your cat is clogged and it will affect engine performance. But if there isn't it won't. If there's too much back pressure at the downstream O2 sensor then the exhaust restriction isn't being caused by the cat, it's being caused by the muffler and that will still affect engine performance. 

Bottom line is if your cats aren't clogged and they're just worn out, replacing them won't affect the voltage signals from your A/F sensors (upstream "O2" sensors) and it won't change how your truck runs. You don't have vehicle inspections so the question becomes, is it worth paying over $2,000 just to get the Check Engine Light to turn off?

......just food for thought



Firstly, thank you for responding.

Again, the truck was taken to a reputable place that had dealt with my friends truck (same year and model, higher mileage). I should've also mentioned that the muffler was replaced a year ago when I first bought the truck.

The report from the shop showed the sensors were operating as they should, but showing that the cats were toast. Judging by how much these trucks rust and how cold Canada gets, there's likely a crack on the manifold (just a hunch).

I see your point about testing the back pressure, I'm not sure I'll have the know-how to do that, but might be worth mentioning to the mechanic who collected the computer data from the o2 sensors.


I would get a quote from a muffler shop but I would first find out what upstream of the CATs is causing the codes.  Overly rich mixture, oil burning, vacuum leak, etc.  If you don't find the cause of the CAT inefficiency, the same thing will happen very quickly to the new CATs. 

I called the muffler shop about an hour later. I didn't tell them of the leak at the y-pipe, but their quote was similar at $2000. Perhaps I should take care of the y-pipe first since I can potentially do it myself and the kit (I was told) is relatively inexpensive. Although, I'm not exactly sure which one I would need to buy as I haven't looked under the vehicle myself.

You still need to find out what is causing the codes before wasting $2k on new CATS, @christian_p

Wouldn't that have been the job of the mechanic shop that I went to to have this problem diagnosed?


The only aftermarket brand I have experience with is MagnaFlow. Had the same code in my Prius, and needed a direct fit replacement. That was about a 100,000 miles ago, and so far so good. 

They don't seem to be too cheap either. Unless i find someone who can cut and weld a universal cat in there, I'm not sure they would be in my wheelhouse.

Posted by: @christian_p

However, they are listed under OE-Design, which I'm not sure if that is a huge deal or not. 

this is mostly just marketing blah blah since emissions equipment is required to meet a standard, but it also means it's going to simulate factory performance, sound, etc. rather than trying to be some high-flow racer-wannabe, wake-up-the-neighbors nonsense.

That’s a good point. It seems opinions are 60/40 in favour of OEM. But I’m also a student and can’t afford $2600 of repairs.

I thought it was the cheaper option

There's technically four options:
1 - I go totally OEM and have the mechanic install. ($3,000+)
2 - I go with mechanic warranty parts ($2600)
3 - I go with OEM-style parts (made in USA) from rock auto and install myself ($1000)
4 - I go with chinese aftermarket parts from rock auto and install myself ($400-500)

I'm probably going to do #3.


One out there option is to go to a junkyard and pull a direct fit from a low mileage similar make and model, or one built on the same platform. But there is no guarantee it will last, and it will be hard to find one low mileage. It may*** be cheaper in the short run, but not sure how long it will last.  On top of that, check state emissions laws to make sure it is okay for you to do this. Same states are more strict than others.

Sometimes you gotta bite the bullet to get the correct fix. 

This is an idea. I am Canadian, so I don't believe they check emissions where I'm from, nor do I plan on selling this vehicle any time soon. I love my tacoma.

Still, I think installing a new unit and hardware will likely be more worth it for the next 10 or so years. After doing research on AP Eastern (Pennsylvania) I'm sure that they put out a quality product.


I have a $600 (incl. labor) Chinese aftermarket cat on my Toyota Corolla.

Works fine, passes emissions - but like many aftermarket cats it can sound like a trumpet 🎺 at mid-rpm high loads.


make sure the cats you’re getting so not sound like musical instruments!

Haha I appreciate your honestly. How long have you had your cats on? Do you remember what brand they were?

About a year, and there are no brand markings on the cats. So far it has been alright.

Did they come with gaskets? I've heard people say "aftermarket is okay, but you gotta reuse your old gaskets. The new ones are junk, etc."

Topic starter

My apologies for not getting around to this quickly, but here's what I did:

(scroll to bottom for summary)

I bought 2 aftermarket cats from autoshack (North American distributor associated with AutoZone) and paid $231.53 + tax, free shipping.

Here's the link to them:

The quality of the cats say "EPA Compliant" for what it's worth, but are a little smaller in diameter from the stock cats. When I inspected the cats, I shone a light through the pipe and could not see anything through the old ones (they had 250k kilometers on them) but I could see a little bit of light through the new ones. 

I installed the parts at a buddy's place which cost me a case of beer and a few hours of my time. The manifold came off relatively easily (swivel sockets and extensions helped) because the nuts are only torqued to +/-25ft/lbs. I was able to reuse the manifold hardware, and replaced the gaskets (manifold and to the rear cat). Everything aligned pretty well all things considered. Turned the truck on and let the oil burn off the new cats.

Check engine light code has not come back after 200 km of driving. I will report back if anything changes, but I also plan on doing a spark plug change (all 6) in the near future, as many people have said that worn sparks are usually the issue.


- I bought cheap aftermarket cats at 10x less the price.

- Installed them myself with a friend (8/10 difficulty, you need swivel sockets and extensions and a good amount of tools).

- Cleared the code and it has stayed off for the last few days.

- I will report back if anything goes wrong.

*A big thank you goes out to all that replied to this thread*


In the states I think I heard after market is OK as long as the emissions are not compromised. Your supposed to keep records and the cat has to be certified by the manufacturer to work on your car. I understand that it is illegal to get a used cat from a junkyard regardless of the fact that it came off of the same model vehicle. I know junkyards don't like to sell them to the general public. I am sure it's done any way.

Correct me if I am wrong.