mb12345

I have a 97 ES300 with 114K miles on it. I have a CEL with P0420 code, catalyst efficiency below threshold. I have replaced the cat twice with aftermarket ones. In both cases, the CEL came back after a couple of months with the same code. So looks like the previous ones were garbage.

In earlier cases, I had the mechanic install the cat. I don't know which ones he was installing. Now, I want to buy a cat myself and have him install.

For those who have had this problem before, and put an aftermarket cat, can you advice on which is the best aftermarket cat to buy that will work and not bring on the CEL/P0420?

I don't want to put a OEM cat from the dealer as it will cost me $1.5K+, so I want to settle down with a aftermarket cat, but of superior quality.

Please advise which is the best aftermarket cat to buy.

Thank you.

Lexmex

I have gone with two different aftermarket converters. The second one was a bit bigger and more conducive to my exhaust system and ram air intake.

First one was a Magnaflow 94005, and then later on the slightly bigger, Magnaflow 93506, which is .25 inches wider (shown below). The 94005 was put on when my exhaust piping was still stock.

Granted this is on an RX300 (which uses a similar 1MZFE), but no such CEL errors.

jon91se

Stop throwing your money away on cats. The odds that either one you replaced before are actually bad is slim to none. My guess is its just tripping because its aftermarket.

jon91se

Not to sound like a jerk but read up.

http://en.wikipedia.org/wiki/Catalytic_converter

There is nothing special about a cat. No moving parts or electricity required. It just burns up excess emissions for a cleaner exhaust.

Hell in FL you don't even need one.

Lexmex

In Connecticut, he's going to need one, they have testing up there.

Lexmex

This is a picture of the two different cats (apart from my OEM) that I have had on my RX300. Mexico wasn't very good to them (high sulfur gas and god knows what else), but I passed Mexico City emissions tests down there.

The one on the right is the 94005, and that was what I used when my RX300 still had its stock exhaust piping.

Lexmex

94005 when it was on my RX300.

mb12345

That is correct; I have to throw money at it just because I don't want to see that CEL on my dashboard and also because I want to pass the emissions test.

Lexmex

I think if you do a search in this forum (I know I have gone over P0420 dozens of times in the RX300 forum) we recently talked about P0420. Wonder if anyone did anything with the O2 sensor after the cat.

The two precats shouldn't be at play here at all. I know people with federal-spec Toyota Solara V6s (1MZFE powered as well) that don't have the two precats, and they go to one of these Magnaflow cats and no codes or any issues come emissions time.

I'd also examine to see if that exhaust gasket (note far left in last photo) is tightened down.

mb12345

I had changed the bank 1 sensor 1 O2 sensor last month, since I had a P0135 then. I didn't change the bank2 sensor1 or the after-cat sensor. Wonder if I should do that? I have discussed this before and was told the post-cat sensor cannot be a problem. If it was, I would have a different code, not P0420. It is highly unlikely that the ecm is reporting a false P0420.

On a similar note, I had replaced the bank1 sensor1 with a OEM sensor purchased from toyota dealership. If I had to replace any of the remaining two, I would want to replace them with OEM as well. Having said that, is the denso sensor the exact same as OEM? i.e. if I am purchasing a densor sensor from ebay or rockauto.com, is it the same (not equivalent, but same) as the OEM sensor?

Lexmex

That's right on your first paragraph. Denso makes the OEM sensor.

I'd have the readings on the O2 sensor after the cat checked out, but realistically for the cost that it would take to check this with Toyota in a diagnostic, if it were me and I'd already changed the cat before, then I'd go ahead and change out the O2 sensor.

DrLex

iTrader: (2)

Before you replace the expensive cats, try an o2 sensor riser first. This might erase the CEL problem.

Sometimes the o2/cat error is just related to excessive heat. The o2 sensor riser will keep the o2 sensor cooler.

I ran into a guy locally that has been through 3 oem sensors @ $150+ each. I find it very suspect that the o2 sensor would just go bad over and over. There is something else at play.

I have Toyota o2 sensors here that are 15 years old and still work fine. Either there is a different problem, or they are using cheaper hardware now.

Toronto

It has been alluded to above, but let repeat/extract some important points.

In Ontario with having emissions testing every two years. After paying for the secondary precision diagnostic, the stock 13 yr old cat converter was singled out.

I did the cheap thing, went to a local muffler shop and they welded in a universal cat converter just south of the flex and some other pieces for about $350. I was mightily annoyed it was welded in, but they argued that is fine in the great scheme of things.

A few weeks later the engine-image warning light came on while zooming along a country road. Turns out the OBD code is P0420 "Catalyst System Efficiency Below Threshold."

On this board, wise posters told me that the ES300 is very sensitive about seeing the OEM cat converter and lights the warning light if the exhaust flow seems even a bit worse. But my light has not come on in the few months since we turned it off. If it does, I will assume it is the cat converter and not worth fretting about.... maybe.

Toronto

Can Lexmark or somebody provide definitive guidance on which aftermarket converters or installation techniques will keep the dread light off?

As mentioned, my dashboard engine warning appeared a few weeks later. Got it read and turned off.

Re-appeared later a few months and is still on. Not good to have it on all the time in case something bad happens for which the signal would be significant (and certainly not wholesome to be on when I face the next pollution test in a year or so because they'll prolly refuse to do the testing).

Wish I could turn if off myself - suggestions?

Lexmex

The converter I mentioned above worked. I am curious as to what kind of universal cat (brand and model number) was used on yours. I am curious as to the size based upon that information.

Was the code still a P0420?