We have a 2009 Toyota Avalon that apparently has a bad pre-cat and main catalytic converter. This is causing codes that are lighting up the check engine, traction control, and anti-lock system lights and disabling the latter two systems. As of now, the car runs like a champ (117k on the clock) and WV is not an emissions state. I can turn off the codes with a cheap reader long enough to pass inspection otherwise. The bitter pill here is repairs with factory parts is north of $1800 to perhaps $2k depending on breakage of old bolts etc.

My main question is does anyone have experience with aftermarket pre-cats and main cats? I’m talking both pre cats (integral to manifold) and main cat for under $300. Do these cheap parts typically do the required job of quelling angry sensors well enough or am I better off just driving what amounts to a pre traction control, pre anti-lock car? The car is a true gem and in perfect condition for its age. All relies are appreciated.

I have not seen cheap cats last long at all, maybe good enough to pass a smog test and sell.

Since the car is mint and low miles it's worth spending the extra for OEM parts if you plan to keep it.

You can put on an O2 sensor spacer to fool the ecm,then then erase the codes.
Only for the secondary O2 sensor.
The secondary O2 is the sensor that determines if the cats are working.

I've used home made spacers and worked with no issues.

Here's a link. If a straight spacer doesn't fit, 90° spacer are also available.


https://www.amazon.com/Generic...id=1784043971&sr=8-1

https://www.minicatalizador.co...LfS5HNBoCnTMQAvD_BwE

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If anybody is wondering why the ABS and TC lights are also on, traction control works in part by manipulating the throttle. Anything that may affect response to said throttle, whether it actually does or not, will trigger the money light.

quote:

My main question is does anyone have experience with aftermarket pre-cats and main cats? I’m talking both pre cats (integral to manifold) and main cat for under $300.

Almost every time I tried an aftermarket cat on a car, it wouldn't fit (one on a Subaru pointed an oxygen sensor directly at a drive axle, jamming the end of the sensor into the joint boot), didn't come with attaching hardware or gaskets, and if I managed to get it on, was still insufficiently efficient, triggering the money light in just a few days. Moreover, two integrated manifolds/cats and the third cat for $300? Even if right, you know what they say about too good to be true.

I'm also having a problem with this "pre-cat" business. There's a manifold/cat on each bank of the V engine, with an oxygen sensor before and after, and there may be a third one behind them. The third one is not monitored by the computer. Unless it is broken apart, physically damaged, or a main cat broke up and blew chunks down it, I don't see why you'd need one.

What codes do you have? The ones for catalyst efficiency are P0420 and P0430. Anything accompanying them needs to be looked at first.

I don't quite understand how your vehicle inspection process works. I gather they'd fail the car for the ABS light. If they don't check emissions or trouble codes, I don't see why you couldn't clear them and drive to the station ASAP. It takes a fair amount of driving for catalyst "monitors" to "run" and flag the cats again. That would buy it some time.

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Originally posted by egregore:
I don't quite understand how your vehicle inspection process works. I gather they'd fail the car for the ABS light. If they don't check emissions or trouble codes, I don't see why you couldn't clear them and drive to the station ASAP. It takes a fair amount of driving for catalyst "monitors" to "run" and flag the cats again. That would buy it some time.

Off topic alert!

In VA, at least, if a car has an emissions system controlled by the ECM or other module, all they do is read the codes. There is no tailpipe sniffing or other physical measurement. The code reader and software they use is proprietary, and said to be unspoofable. This software manipulates the throttle and, presumably, other parts of the engine during the test. Older cars have to go through a dyno+tailpipe examination unless they are old enough to be exempt.

We also have drive-by stations usually placed on on ramps that allow one to "get inspected" while doing your usual driving. I am not certain exactly how they work, but logically, some sort of air quality monitoring would be employed.

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2009 Toyota Avalon

Odd that both cats would be bad at the same time, suppose it's possible, have you had anyone look at it and make sure it's not a bad 02 sensor.

My F150 was setting those codes and it ended up being the post cat sensor was bad on one side, once we replaced it the codes went away.

If a manifold cat is coming apart, the debris will pulse back into the cylinders on that bank and dust the cylinders.
You need to read fuel trims (cheap code reader should do it), if all the trims are at near zero, fix it right, cheap parts are going to bite you in the ass on this one.

You can't just clear the codes and haul ass to the test station.
The system takes a bit of driving under various conditions to enter a ready state after clearing codes.
If it's not in the ready state they will tell you to come back.
Most code readers can tell you if it's in the ready state or not.

Thanks for the replies all- the car sat for some time after the older previous owner passed away. It’s possible the main cat is toast from moisture damage as the technician said he heard rattling inside it.

This is my son’s car and he’s actually had a valuable learning experience learning how to threshold brake and judicious throttle control. When we get it fixed, we’ll likely bite the bullet and stick to oem.

My Ford needed a new cat and I was getting price quotes north of 1200.00. Went to Rock Auto and picked up what I needed with new O2 sensors for about 300.00. Found a guy who just did exhaust systems and he agreed to do the install for 100.00. I was out about 400.00 and passed emissions.

I own a (not shade-tree) auto repair shop, and within the past year we made the decision to not use any more aftermarket catalytic converters. My margins are WAY lower on an OEM cat, but come-backs are all but non-existent. We have a supplier locally who will give me a lifetime warranty, including labor coverage on their aftermarket parts, and its still not worth it. Any aftermarket cat is near-guaranteed to fail, and chances are, it will only kind of fit. If it comes with gaskets, they are garbage, and it is almost guaranteed not to come with hardware.

Save yourself a load of headache, and just buy the right part in the first place.

Also, make sure that whatever killed the first converter is repaired. They seldom go bad without some outside influence.

Issues that can kill cats include
(1)poor air-fuel ratio control
(2)certain engine oils that burn inside the combustion chamber due to lack of ring sealing or valve guide sealing
(3)years of driving with "convenience store" fuels that do not keep injectors clean
(4)repeated cold starts without a sufficient drive cycle after each start

All these reasons are from extensive laboratory testing experience.

^^^
Could this include accumulated moisture in the cat over a long period as well? I believe the car sat for some time after the previous owners passing. Other than that I know nothing of their driving, fueling, or additive practices.

Our 2012 Jeep Liberty crossover/cat pipe developed a rust hole, short trips, 50k total miles. I had a local shop patch the factory one vs. using an aftermarket cat. Seen too many aftermarket cats fail, some right ou of the box.

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Originally posted by gearhounds:
^^^
Could this include accumulated moisture in the cat over a long period as well? I believe the car sat for some time after the previous owners passing. Other than that I know nothing of their driving, fueling, or additive practices.

No, this should not have any effect. The whole exhaust system gets pretty full of condensation after a car is shut off.