Can the experts please tell me if my RX8 might have a chance of passing California smog with a P0420 CEL (which probably indicates a bad catalytic converter or O2 sensor)?

I've already read a bunch of threads, with the most relevant being the following two:

https://www.rx8club.com/showthread.p...ytic+converter

https://www.rx8club.com/series-i-do-yourself-forum-73/diy-gutting-out-your-catalytic-converter-108878/

I've been driving with the CEL for over a year. The CEL will come on for a few days and then disappear for a few days, back and forth. I bought a used OEM catalytic converter with low miles and I plan to install it. BUT first, I thought I might just take my car in "as is" to see if it can pass emissions with the old, original cat.

Although the CEL was first triggered over a year ago, the exhaust smell doesn't seem overpowering or different than when I first bought the car in 2003. Sure, on start-up, it's really smelly (normal) but it doesn't smell much when warmed up and idling after a long drive.

So I'm wondering if this means that the catalyst material AFTER the rear O2 sensor is still functioning normally and effectively (as StealthTL discussed in the 2nd thread listed above). If this is true, is it possible for my car to pass California emissions? (I understand I need to wait for the CEL to turn off or do the ecu reset to turn it off BEFORE I bring my car in for smog.)

Thanks in advance.

 

Well, do they hook the car up to their computer? If they do, and it has a code, it will fail.

 

But like I mentioned, I can do an ecu reset to make the CEL disappear before I take the car in for smog.

 

It won't pass if you've just cleared the memory.

Ken

 

Ken, do you mean that a smog test will look at the readings between the two O2 sensors as opposed to simply sampling the "cleanliness" of the exhaust coming out?

I guess what I'm asking is: What exactly is done during a smog test? And why won't the car pass if I clear the memory?

 

There are what are called "monitors" programmed in your PCM. The PCM performs certain tests of you emissions systems while driving (and even when off). They run almost every time you drive your car. If you clear the PCM memory, the monitors reset to a "not ran" state. The smog check computer scans the PCM memory and checks to see if there are any codes stored and if the monitors have "ran". If they haven't ran you will fail, the smog tech will tell you to drive your car more....so you do and then the check engine light will come on because you have a bad component.

It's a system designed to stop people from doing exactly what you want to do, because that is what people were doing before OBDII!

I would try to repair your problem then make sure you reset the memory, drive your vehicle a while so the monitors run, then smog it. No check engine light means your car "should" pass.

I don't see a P0040 in the workshop manual. You should make sure you got the right code before troubleshooting.

 

Exactly what I needed to know. Thanks.

BTW, it's a P0420 code, not P040. Sorry, my mistake.

 

Ok, that does sound like a cat!

You MAY pass the smog test during the time your check engine light is off (if your not resetting the PCM yourself or disconnecting the battery). The PCM turns off the light (but keeps a pending trouble code) after I think two times of it passing the monitor in a row. You will not fail for a pending code, only a "hard" code, which means the check engine light is on. Your cat is probably right at the limit so sometimes it passed the test and sometimes it doesn't. The actual smog test is easier to pass than the on board monitor so don't worry about the tailpipe portion really.

No guarantees though. Your best bet is to get a CAN enabled scan tool/ code reader that way you can make sure there are no problems right before you bring it for smog.

 

If you reset the codes, you can't just go get it inspected because the CEL isn't on. The ecu needs to go through it's normal test cycle to determine if everything is fine. During this time, if you try to get it inspected the station will get a message saying not ready and they won't inspect it. IF your car reaches the ready point and no CEL comes back on, then you can get it inspected. However what will most likely happen is that you will finish the test phase and it will throw the CEL again stating the problem is still there. Get it fixed.