I had the VSC and check engine light come on. I had the codes checked. The error codes read were P0430 Catalyst System Efficiency Below Threshold (Bank 2). This code came up twice. It was the only error code indicated. I had a reputable local muffler shop check it. They checked the exhaust system and said the catalytic converter and downstream air sensor were good. They suggested that something in the engine may be the problem. They mentioned that a bad seal could be letting coolant into a cylinder. This was beyond their expertise. I assume the checked the rest of the exhaust system, but I did not ask.

Any ideas? If I clear the codes, things are fine, unless the RX330 drives continuously for about an hour. The VCS light and check engine light come on. I'll get a new read and again, the P0430 code is the only code that will come up, but it again will come up twice when the codes. I have read about a "Y" pipe, could this be an issue?

I'll shut up and listen to your thoughts.

Thank for the help.

 

Do you use regular gas? If yes then try mid or premium...

 

actually these second gen rx's require premium per a label on the filler door.

 

No. But I use premium (from Costco) since the min allowed octane number by manual is 1 point higher than octane number of regular gas in my state

 

I usually go with the 87-91 octane depending what's on the bump. I did some addition research, could it be a hole in the exhaust pipe ahead of the sensor? Or the exhaust manifold or the cylinder head?

 

If I understand correctly, 2004-2009 is considered second generation and I don't want to derail the OP/thread, but the premium fuel statement is not true for the RX330. Concur it is correct for the RX350 models.

Since the OP has RX330, I just wanted to clarify -- the owner's manual extract is below (note: it does go on to say "for improved performance, use 91"). We are at 261k on ours with 85 octane.



For the OP, have you tried the spark plug de-fouler trick?

 

well mine has premium fuel only on the label inside the filler door. So I guess the 3.5 in the second gen rx350s were designed for premium only and the 330s were designed to run on regular. Which kinda sucks i wish they would have made it so the 350s could use regular as it would sure save me some money every fillup.

 

wow!!! thats amazing!!! 261,000 miles and still going!!! i hope mine gets to that point and then some!

 

it doesn't really affect your pocket - lower octane gas with lower price has lower mpg.

 

I have used regular like maybe twice though and yes it did result in lower mpg.

 

I've never heard of this. Please let me know what it is. I did top off with premium gas and add a bottle of Lucas Oil, high mileage gas treatment-fuel injector cleaner.

 

I don't know if you are referring to my post, but if you are, google "de-fouler" or "non-fouler" as related to the sensor you are getting a code for. I have never tried it, don't know anyone that has and have no idea if it works, but the concept is interesting.

 

Replace your O2 Sensor, in your case the downstream O2 sensor, Bank 2. $50 O2 sensor will fix it. Plug and play.

 

I’m a recent owner of an ‘05 RX330 (acquired @ 223k) and as I was crawling into 230k mark around a week ago, where I got this code also. I had the CEL, VSC, and TRAC OFF lights. I recall reading a Lexus thread where a tech chimed in and said 95% of the time it’s the bank 2 cat (other 5% could be the sensor). I was thinking about buying a California approved magnaflow cat, but I saw a somewhat free version, which was Italian tune up. They recommended to erase the codes and go on the freeway to see if it reappears.

I didn’t erase the codes and mysteriously a few days later on the freeway all the Christmas lights disappeared. I think maybe if it’s not the O2, then the rear cat going bad? I believe the RX330 has 3 cats - one on each exhaust manifold and one on the rear. So I believe code P0420 would be the manifold one, while P0430 relates to the rear cat (bank 2).

 

Sorry to double post. Lights have been intermittent since 230k. Currently at 231,300 and added Cataclean from walmart for $25. I’m not one to use liquid mechanic, but worth a shot instead of ordering a 50 state approved cat that’s “on sale” for $500. They recommend adding when 1/4 tank or approx 4 gallons. I added it and drove highway 15 miles and then filled the tank with Chevron premium (usually jump between Costco gas). I will post an update on my next oil change around 233k.