delinquent543

what are the symptoms of a clogged of non-functioning catalytic converter? i get the SES code for non functioning cat, but idk whether its a clogged cat or a broken o2. any way to tell? thanks

GT Griller

iTrader: (8)

If the code reads, below efficiency then its probably clogged, i dont think there are really any symptoms, i know mine wasted a just a little more gas but thats it as far as seat of the pants feeling, it alos ran .2 slower at the track.

BlutVonSchwachen

iTrader: (7)

If it was a broken o2, you would be throwing an o2 code most likely.

If you have a pressure gauge, plug it into the pre-cat o2 sensor and turn over the car. It should be around 1 1/2 psi. If it is more than 2/3's that indicates a clogged cat. If you feel it may be an o2, just switch them around and see if the code stays. (remember, 40 warm up and cool downs are usually required to get the dtc to reset.)

delinquent543

well, after scanning it at autozone, i found that the error was P0420 Catalyst System Efficiency Below Threshold (Bank 1). does that mean that the cat on the driver side is actually busted or is it just the o2 sensor? Does this code only come up with a busted cat, or can broken/dirty o2 sensors trigger this too?

JL ws-6

iTrader: (50)

What is done to your car? I had that come up after the first time the car was tuned.. because the richening was messing with it. I had longtubes on teh car at the time, LM catback lid, pulley.

BlutVonSchwachen

iTrader: (7)

Running rich will damage the cat. Produces more heat to burn the extra HC, and the cat wasnt designed to with stand that extra heat.

Silvrshark

It don't appear that the question was answered. I just got back from auto zone with a code P0420, the Pcm has determined that the catalyst system efficiency for bank 1 is below threshould for the current engine operating conditions (bank 1). the guy at auto zone said it was a rear O2 sensor my mods are listed below. Don't know if he is correct or not.

Starz T/A 17

iTrader: (6)

What are your mods? As soon as I put my LM and Lid on I threw the same code. seems a little too odd for it to happen at the exact same time. I talked to a few mechanics and a few suggested that It was flowing so well through the cat that it was throwing a cat code. I just got 02 sims and it fixed it

2001NBMZ28

P0420 on a stock setup is probably a bad drivers side cat. Happens alot, they're covered for 8yrs/80K under the federal emissions warranty.

JL ws-6

iTrader: (50)

Could be a o2 sensor, easiest wayt o find out is to pull the o2's on the drivers side and swap them with the passenger's side, if one is bad it will show up on the other side, or bank 2.

If it comes up again on the same side, the cat is most likly bad. If you are planning on headers and a new y pipe, do it now and get a tune, problem solved. nothing worse then spending $ to fix something that you are gonna end up replacing anyway.

Check your MAF to while you are at it, make sure that lid is sealing good, if it's not and it got dirty, that could cause goofy maf readings, leaning, or possible richening the car up too, I have seen that happen before. Most likly not it, but could be the problem.

Aegnor

Low Efficiency would seem to indicate that the rear O2 is reading too much (or not enough, not sure which it wants) oxygen after the cat, thus leading to the PCM assuming that if the front and rear O2 sensors are working properly that there isn't sufficient change in the gasses passed through the Cat on that side. Could still be a bad O2 sensor though. It doesn't sound too much like a clogged cat.
The cat on my old Camaro (94 V6 3.4L) got clogged once and the car would choke itself after about five minutes of running. The gasses of a fully clogged cat will quickly backup in the exhaust track, preventing the cylinder from being able to push them out when the valve opens. I was lucky to be able to limp the car the half mile to a shop that could fix it. I would think that if your cat is clogged, your car would have very little power and you would notice a big difference in performance.

Jimmard

iTrader: (12)

Yesterday when I was driving my car, something started rattling underneath my car. Took it to an exhaust shop and the guy hit my passenger side cat and it made a bad rattling noise, he said it was bad. Took it to the dealer, made an appointment and I assume they will fix it, (02 ss with 27k miles on it). My only question is that because mine is rattling really bad I assume its not clogged? Im guessing something broke off inside and its rattling around. So it should be safe to drive for now? Also wondering if they will blame it on the fact that the pipe leading out of the passenger side cat (the one that went bad) was scraped from bottoming out and blame it on me and make me pay to fix it. Or could they blame it on my aftermarket cat back, or even the cutout? Thanks.

James

273sunsetZ

Mine was clogged for sure.. If you can smell exhaust fumes, like when you stop at a red light, than it's probably clogged or bad. My cats were bad and i kept replacing the o2s, and they kept going bad, finally it hit me that mabie the bad cats were causing the o2s to go bad. Finally junked them.. LT-ORY..