Hey guys, I have a 2002 Lexus gs300 and I got the same problem. Have the same p4020/p4030 code low efficiency bank 2. I was told to change the cat converter. I got the aftermarket one and after like 3 weeks the same code popped up:(
I returned that one and got a used but original one from the guy who crashed his car. I had that one installed and got the same code .So I am a little relived now because I found this post, thank you for that. I have been to 3 garages and they could not figure this out.
I remember that one of the mechanics said that I have a leak but they also said that a leak will not cause a cat code come up. Anyway had my car lifted today and I don’t know where is the leak from but i can hear something is leaking. It’s under the heat shield and it’s after the front cat converter, I believe it’s the back cat converter pipe that connects with front cad converter. This other mechanic told me that he can weld the hole but if he takes the heat shield out, it’s all rusted, he will not be able to put it back, and he does not want to leave the pipe without the heat shield as the pipe is right next to gas plastic back feeding pipes and that is why he did not do the work. Do you guys know what I can do besides just buying another cat to replace that piece of pipe?
Can I get just the heat shield or any other ideas what i can do but just buying the whole piece with the back cat converter? I have already spent a lot of $$$.
I really appreciate your help.
Thanks
