Mkot9

Hi. I joined a few months ago when I bought my car and have only been on to read information. That said, I have a 2005 RX330. The VSC check engine lights have been on and off since about three days after I bought the car. I'm confused because the manual says that VSC is "variable stability control" and has to do with brakes, etc. working in case of collision. I read on this club's website about what it really means. I went to Autozone and used the OBD magic wand and it came up, as stated here, PO420.
My question is what things should I check first instead of the Catalytic converter? I use only 91 octane, not always from the same station or brand. I have read to clean the converter, spark plugs, O2 sensor, gas line cleaner, etc. I am honestly hoping it's just something that I can do cheaply like Caticlean. I need new tires, don't know why, and new brake pads, don't know why, and that's already a big chunk of change.
Can anyone please tell me all that needs to be checked and what it is MOST LIKELY, please? I can do my own repairs but I just looked at the price of an O2 sensor and wanted to run!!!
Thank you for any and all responses, I'm hoping for a miracle!!!
PS What the heck does VSC have to do with emissions anyway????

mandyfig

1st task is research what P0240 fault means, lots of videos. Knowledge is a good thing.

Like this link (there's a lot of them):

https://www.fixdapp.com/blog/p0420-toyota

phimane

I would also suggest getting a Bluetooth/wifi OBDII adapter to use with your android/iphone so you can look at live data. They are cheap and the apps are too. Knowledge is indeed a good thing. You could potentially find out if you CAT is bad or not yourself. Lots of Youtube on reading live data and CATs. Live data is powerful.

Varuun

Had same code 2 months ago. It was the front catalytic converter clogged up. Spent 400. And now its all good.

Adam200699

Did you replace the catalytic converter? I was quoted much higher for replacing the front cat.

Varuun

no I went to the mechanic. I am not technical enough to replace by myself.
he was reasonable. just ask around to local mechanics. don't go to the dealership.

Mkot9

Thanks. I'm hoping to clean it out with a can of Caticlean, hoping! $400 is waaaaaay more than I want to spend right now. I have a couple other car things to take care of and a new cat con or a large bill for cleaning it would bury me.

Mkot9

Wait, I just read the other two answers. There's more than one? I've been so busy with other things that I really haven't researched it yet. Rats!! I better just lock myself into a cave and get a bit more knowledgeable on this vehicle! After all, it's not my 85 Toyota pickup! I wonder if there's a "Lexus Fairy Godmother" who would grant my wish?
Thanks for your help!

Adam200699

About two years ago, my 2005 RX 330 started check engine code P0420. The cheapest quote I got for replacing the catalytic converter in my area was $600. I did not fix the catalytic converter, instead I bought a O2 ($10) sensor extension, and the code never came back. I put another 30k miles on the car, and did not notice any problem. Two months ago, I noticed a strange vibration noise from the front of the engine at idle. I have two mechanics look at it. No one was able to find out where it came from. The cars have other long term issues, small leak in radiator, front transfer case was leaking, front struts, abs sensors all need replacement, and I'm due for replacing all the tires. By the time I add up the number, it wasn't worth the repair. I finally sold my RX two weeks ago, and she has close to 200k miles on odometer.

marwin

Good day! I just want to share my experience with this code. It could be caused by vacuum leak, from cracked hoses (vaccum) to old gaskets in your air intake system. Also changed pcv valve. when those didn’t worked, I moved on to the exhaust, replaced the gasket on the y connection after the rear O2 sensor.then my last was to change the AF sensor and the rear O2 sensor.i used the denso brand.now after 3 months
the code is gone.
By the way I only have P0420. I did all the work myself and spent less than $300. One more thing, i noticed that all the parts I replaced were all from when the vehicle was built so they were old.
With regard to AF sensor and O2 sensor live data reading, I was really not sure if to change the sensors bacause i only have p420 not p430. and when i compare the readings they were the same. (voltage).but i did notice that the sensors for the bank 2 was replaced, (this is in the front so maybe the reason it was replaced. convinience. bank 1 is harder.a lot harder). so as a last resort before even thinking of replacing cat converter, i replaced the bank 1 sensors.
ps. when i say the voltage reading, before i changed the bank 1 sensors, the air fuel sensors on both bank will read 3.25 with changes when u press on throttle.so u wouldn’t think of any problem there.and then on rear O2 sensors they were both oscillating between 1-8 volts.both of them. but i only have p420 not p430. so i thought they were not the problem.
but when i changed the bank 1 sensors the voltage reading for both rear sensors became stable.if i remember right around .7v, not sure but both became stable.

Turbo123

I have the same light on as well I plan on doing a tune up as well Ngk double platinum plugs .Lexus valve cover gaskets
New PCV valve .
Where is the best place to buy spark plug wires or coil what ever name you prefer .looking on line can really be confusing on what to trust same thing with 02 sensors
Mine is a 2008 with 110,000 miles.
Anything else I should do while in there ?
Thanks.

tomr51

rockauto.com are good

Turbo123

I was on rock auto site how are the Denso Coils?
Goodwin o2,s allmost half of Bosch? Any suggestions on what to buy on those brands?
Thanks.

marwin

turbo- i forgot to mention mine is a 2006 rx 330 with 3mzfe.im not sure we have the same engine but if u are going to take off your intake plenuum better have all the necessary gaskets, e.g throttle body, intake plennum, and vaccum hoses in case u see some cracking.
when i buy parts, i check lexus websites for part number.and then try and compare prices with other sites.most of the time i buy from rockauto and look for parts details for compatibilities with the number u get from the lexus websites.rockauto is cheaper than amazon when same products are put side to side.it’s just the shipping cost that kills at rockauto.be patient when comparing prices and you will save a lot.
with electrical components, i have read alot about failed parts because they are too cheaply made.so i always go with oem or denso since they are oem manufacturers.
i would assume ur lexus would have iginiton coils and not the wires that the old ones have ( distributor type) but if they aren’t giving u issue, i wouldn’t change them. they are expensive.if spark plugs are still the orig, i will change them all 6 of them. i would be careful with what kind of plugs i would put in.as wrong type can cause trouble codes.also if the clips on the coils are brittle, securing them with zip ties wouldn’t be bad.it would be inconvenient if they got pulled out during driving.
with p420 code, if ur engine is still strong, i wouldn’t condemn the cat yet.i almost did.try to fix everything starting from ur air filter housing going to the cat.that is what i did.and since the engine is not new, it is like giving it a tune up.i have read somewhere that lexus engines are not forgiving when it comes to vacuum leaks.i also saw a video where the guy just dismantled and reassembled the air intake system after the engine got codes when he changed spark plugs.it was a v6 so he has to take the plennum out. and that fixed his problem.
one last experience to share, i am one of those who believe that silicon containing gasket maker can damage O2 sensors.it happned to me.

marwin

turbo123 if u can invest on a good obd reader with live data.it will be your best friend on this p420 journey. a lot of reasearch and patience will be your best friend.
the vsc code will always come on whenever the p420 comes out.so fix the p 420 first. and also a lot of people have said, take a look at your fuel trims.good luck