Bad Cats but passed CA smog

[RCodePaul]

I've had a CEL for a long while due to the "cats underperforming" code. I was told (incorrectly) that only OEM cats are legal in CA at $2k, so I held off. When I clear the CEL it will stay off for a day or two before it is triggered. Car seems to run just fine. It's like the calibration for the error is off.
Just got my registration renewal and had to have a smog check.
Cleared it, took it to smog check.
Pass.
CO2 14.7, O2 0.3, HC at 13 (max is 49) CO .02 (max is 0.47) NO ppm at 52 (max is 409.)

So, either CA smog limits (with dyno/sniffer) are a joke or the LS OBC is way sensitive.

Also, saw this today

...it started missing, and got bad very quick (less than a half a mile). the CEL never came on steady or flashing, as i pulled into my parking lot i gave it a hard pedal press to see if i could get it to kick a code so i would know which side of the motor to start looking at and instantly the CEL started flashing and the car went in to fail safe mode, so i coasted in to my parking spot. then after i shut it off i could get it to start again but it would just die in seconds because the cats were completely clogged. not fun, i'll tell you that

Last year my LS would start and die exactly as described. Went through the COP deal before that. Called a buddy and read the codes. Had the cats error code (of course) but also threw several other codes including a TPS code. I thought, well, I will have to break down and do the cats, maybe a throttle body since the TPS isn't available separately.
He said before throwing parts at it, let's reset the OBC and see what codes it throws. While we were at it, we removed and cleaned the throttle body. I was still convinced the cats were clogged.
Cleared it, reassembled it and the problem vanished. Only code to reappear (days later and while running just fine) was the cats code.
Go figure.

 

[Alax7]

Congrats on passing. OEM cats are not the only legal cats, you just can't replace the cats with just any cat, it can't be move, can't be high flow and has to be installed by an approved shop, they have to sign a paper, you sign a paper, and all this other bull

 

[drag214]

I just got smog for my 2002. Your output readings are normal. I had the exact same readings. It's a possibility that your cats aren't bad. When my cats were bad in the 2000 LS, the restricted exhaust circulating around in there heated the pipe some much, they were glowing orange. I also had that awful rotten egg smell.

 

[Mechanicboy]

Your rear o2 sensors are probably bad. What I don't get is how you passed without that monitor running. The ls must not run that monitor until the very end because you are alllowed a couple monitors to not run and still pass.

 

[RCodePaul]

Love the idea...

Your rear o2 sensors are probably bad. What I don't get is how you passed without that monitor running. The ls must not run that monitor until the very end because you are allowed a couple monitors to not run and still pass.

Thanks for the feedback, although the monitor bit's a tad over my head - but I'd be ecstatic if that were the case. When the CEL comes on, I've not had an o2 code yet.

More than happy to test the o2 sensors and see if they are the culprit. My Ford Shop manuals are at a buddy's house so I can't look it up today. Is there a simple resistance test or similar I can do?

 

[Mechanicboy]

There's not a simple test for the o2 sensors unfortunately. I had a simular issue with a 99' camaro I bought recenty and ended up finding out it was the cat so I put the old sensor in and figured out how to trick the o2 sensor into believing the cat was good by modding the signal that comes out of the rear o2 sensor before it gets to the computer so it never throws a code and there's nothing visually a smog tech could see. I did it this way because you can get fined for tampering with somg equipment in cali and it's an automatic fail of the smog test. While the fine is rare I really needed to pass the visual because I didn't have any friends in the smog test business at the time so the non-fouler trick wasn't an option for me.

If you're not getting o2 codes than I wouldn't mess with the sensors. However I would fix whatever your other codes are. A good rule of thumb is to always fix the non emissions codes first because they could also be causing the emissions codes.

 

[pragmatic]

Your rear o2 sensors are probably bad. What I don't get is how you passed without that monitor running. The ls must not run that monitor until the very end because you are alllowed a couple monitors to not run and still pass.

I would think it would be the front ones that were no good. To see if the Cat is working the ECM is looking for the front O2s to be switch faster than the rear one (once the exhaust is hot enough for the Cat to work). I would think that a new O2 would respond quicker than an old one.