---2000 GS400 w/116k miles---

P0430 - Catalyst system Efficiency Below threshold(bank 2)

Google'd and got three main issues.
1. Exhaust leak
2. Converter bad
3. o2 sensor

Just wondering from you guys what did you do to fix this problem when you had your P0430 CEL? I read online one guy said his throw this code, he put new plugs and it was fixed. The rest of the reviews I read was the three main issues above. I'm not sure at this moment what to do. Dont want to spend $$$ if I dont have to(for buying cat when its o2 sensor, or the other way around).

-How should I start(besides checking for leaks)?
-Which sensor is BANK 2?
-How can I fix this?
-Should I start with a new o2 sensor? which one(bank2)?

Car drives perfectly normal. No hesitating, starts fine, no performance lost...etc.

 

Start with the cheap stuff first.

Check for exhaust leaks. That's what my problem was. Fixed and the CEL has been gone for 7+ months.

 

If there's a leak most likely where does it leak?

I bought the car with a Carson Tuned Exhaust system. I'll check the whole exhaust system tomorrow morning when its not so hot & humid outside. It'll be great if I know which or where is the sensor that is throwing the CEL that way I can pin point closer to the issue. That reminds me of another Q, I'll check but just curious, how many o2 sensor does my 00 Gs400 has?

 

Check it at the flange after the cat and before the down stream o2 sensor.

I believe our cars have 4 o2 sensors - 2 before and 2 after the cat.

 

alrighty, will do that first thing tomorrow(tighten bolts) and turn off the CEL see if it comes on again.

thanks

 

Here are pics of my flanges. The gaps looks big but when I shine my work light in it it actually is still sealed. Maybe not 100%? who knows. I'm putting some high-temp silicon gasket maker on it now leaving it overnight and seeing if the CEL comes back tomorrow when I drive. *Crossing my fingers*

Shot of the Driver side exhaust right after the cat.


Passenger side exhaust right after the cat.


Looks to me like its 99% the problem. Any thoughts?
Even the other side of the flange, facing the vehicle, has this gap too. Both driver & pass side. I'll go new gaskets if the silicon doesn't work well but for the look of it I may need new bolts if I take these rusty bolts out.

 

Did you start it up and feel around for air?

 

Start the car up and see if you can feel any exhaust escaping at the flange(s). If not, replace the O2 sensor(s) and finally the cats. Be sure you reset the ECU after you make every change.

 

^..yea but the Q is which one? which is BANK2?

 

Passenger side of car. Standing in front of the car, facing the car, the left side.

 

passenger side

 

BINGO!!! Gap on the driver side is leaking exhaust.

Just put High temp silicon on the gap yesterday and drove it today. So far so good, NO CEL's.

Once again, thanks a lot guys...and thanks for that pdf file ^...that comes in handy for future reference. Problem solved(at least for now).