Brave777

Hi Experts,

Newbie here. All though I'm a die hard Toyota fan. My father retired with GM and celebrated the next day by buying a Toyota!

I've got an 01 Tundra with 170k and no trouble. And a 01 Highlander 4 cylinder with 330K and no trouble. We just added a 04 RX330 with 170k on it. It had an impeccable 15 page Lexus dealer history.

That said, I had the check engine, Trac off, and VSC light come on about a month after we bought it. I used my acton scanner cleared it out. Then I noticed the gas cap was loose so I attributed the issue to that.

Yesterday, the lights came back on again. I have not cleared the code this time. My scanner is showing a "P0420 Catalyst Efficiency Below Threshold Bank 1" error. This car has a brand new cat installed by the Lexus dealer about 6 months ago.

I saw the buttons below the dash that say Trac off on them.

Can anyone tell me what I need to do here? I've been reading various posts. Just not sure if what I am experiencing is the same as the other threads posted.

Thanks!

LSBen

The RX330 has 3 converters, 2 manifold converters and 1 catalyst converter. Did the dealer replace 1 or all 3 converters?

crimedog

Mine had the same codes when I bought it. The guy I bought it from was told by the Toyota dealer that it needed new catalytic converters.

I didn't know how old the spark plugs were (192,000 miles) so I decided to change them. In the process, I also changed valve cover gaskets, cleaned the MAF sensor and also the pcv valve. The pcv valve is a known issue on these vehicles. Mine was definitely bad.

Trying to make a long story short, the code is gone and hasn't come back in almost 6,000 miles. I am pretty sure it was the pcv valve, but I guess it could have been any of the big three (pcv, spark plugs, MAF) that was causing the code. The spark plugs were pretty worn and I would assume the factory plugs.

thegrouse

That code is for the cat between the engine and the firewall. I did a write up when I changed mine

Brave777

OK. I'll look it up. I'm pretty sure that is the one that has been replaced. Still trying to find out. If I don't get any where after the spark plugs, and pcv valves, I'll look more into the cat. Thanks.

Brave777

I just replaced the spark plugs with new recommended Denso's. Also replaced the PCV with an OEM part. And cleaned the MAF sensor and throttle body. Prior to replacing the parts, I cleared the code with my acton scanner.

After all that, the lights came back on several hours after the parts replacements. Then the lights went off yesterday and stayed off for 4 hours. Then they came back on.

Any idea what to try next?

crimedog

If it were me, I would do a search on "cleaning the catalytic converter". There are several methods on youtube using different chemicals. Some you drill a small hole in the upstream part of the converter and spray fluid into it and run. Others you add to the fuel tank.

At this point changing the catalytic converter is going to be a little pricey. I am cheap so would try to clean the material in the converter before I replaced it. I have no experience with these cleaners so take with a grain of salt...could be a waste of money, could possibly cause damage to the engine. Do not know.

Brave777

I'll hold that off until I get more desperate. I have not replaced the MAF or any of the sensors yet.

numbafree

It's either the sensor or the cat. new cat, it's gotta be the sensor.

brianmch

I am having similar issues. Codes read for O2 sensors but that shouldn't make the lights stay on, should it?

Brave777

You guys won't believe this. Even I don't. I just did a full flush of the transmission to include flushing out all fluid, replacing filter, replacing gasket, and cleaning the pan. After I put it all back together and added the new transmission oil... my lights have gone off. No more CEL for 3 days now. I checked the codes and was getting the p0420. If you can tell me how changing the transmission fluid helped clear a p0420 code... I'm listening.

crimedog

Gotta be a coincidence, right? That's really strange. Keep us posted if the code comes back.

taldrich97

I own a 2006 RX330 with 214,000 miles. CEL and VSC lights used to come on now and then. Now they have been on for a few months. I went to Advanced Auto and they read codes of P0420 and P0430. The guy was trying to get me to go to the shop he also works at so he wasn't very helpful in giving me any more information as to what may need to be replaced... How do I determine what the codes mean?

Thanks,
Tom

HomeinMass

I bought my '04 gs300 with the vsc and cel lights on. For some reason, when Autozone checked the codes it came back for (6) o2 sensors and one other code which I can't recall. The car only has (4) o2 sensors; 2 upstream, 2 downstream. Autozone wanted $80 -$120 for each one. I found all 4 on Ebay for $84 total. I managed to change 2 with the wrench I had but had to rent some sockets to release the others. All said and done, no more lights and no more hesitation on take-off. So if you need some tips to change them, let me know.

Brave777

Well... the light is back on. No idea why it stayed off so long.
I did try to install O2 extenders. But there was not enough clearance even with a 90 degree elbow.

I'm now down to the O2 sensors and the cats. I have used my scanner to check the sensors. Both show fluctuating voltage. I'm told that means that are good. But I'm not totally confident in that.

Does anyone have the Denso part numbers for the O2 sensors?

The original owner just told me he had replaced the front cat. When I look on RockAuto it looks like they have a "front left", "front right", and "rear" cat.

Mine is a Japan Built, FWD model.