My check engine light came on about 3 months ago, and I had it checked out. It said catalytic converter bad. I have been told this does not always mean the Cat itself. Could be something else. Also my mechanic turned off the light and it has never come back on again. I’m going to check in on a new converter, but have been told the warranty on a cat has to be checked by a product representative, because a misfire can cause a cat to go bad. I’m wondering if perhaps a plug or plug wire went bad. Is it okay that the car was driven a short distance or does just one misfire ruin cat immediately? I’m really confused. Cats are really expensive. Thank you all, Ronny. P.S. The car is a 1996 Toyota Corolla.
Its true that a code that detects cat inefficiency does not always mean it the cat. Those code come from comparing the front and rear oxygen sensors. The purpose of comparing the two sensors is to see if the cat is working, but there are other things that could cause the sensors to indicate a bad cat.
One of the sensors could have a problem. You could have an air leak in the exhaust system. You could have gotten a little water in one of the connectors for the O2 sensors, or it could have been a temporary anomaly.
If the light has not come back on, you need to have your mechanic check the system with his code reader to see if all the parameters have reset. If they have, then you are good to go and you should not do anything.
One misfire will not ruin a cat. If you allow a misfire to occur for sometime, then it will destroy the cat. You probably wouldn’t let a misfire go on for long as the car will run very rough, power will be reduced and gas mileage will go down.
If you haven’t replaced the plugs in sometime, then you need to check what type plug your car uses, check the owners manual for the service interval recommended for changing them and if it looks like it might be time, then replace them. That will help insure that you wont have a misfire, not a guarantee but at least it will reduce the chances significantly.
"Also my mechanic turned off the light and it has never come back on again. "
Go get your smog test and drive on…
Do you take your car to a “test-only” station? You might not have to, check your registration paperwork. I am pretty sure that test-only stations are for cars older than yours. The test-only stations are more difficult to pass. Also, the federal warranty on your cat has expired unless you are talking about a manufacturer’s warranty.
I am assuming your mechanic reset the computer. You will need to drive for at least about 40 miles and reach a speed of about 60 - 65 mph to “erase” the computer’s memory, then you can try passing the test. Since the CEL was on 3 months ago, you should be good, unless only the light was disabled. Virtually all stations give a free retest within 30 days if you fail the test. If your registration is coming up very soon, I’d recommend doing the test to see where you’re at. (I had some issues but was able to barely scrape by the emissions test for several years.) If you fail, you can fix whatever you need to fix and try the test again or if you still qualify for the warranty, get that new free cat. CA has a program where if your car needs repairs above X dollars to pass the test, you just pay a fee and they let you keep your car. Also, I believe there is a program where you turn your car in and CA pays you $1,000 for it (it has to have been registered in CA for the previous year). Any test station should have the forms and pamphlets available.
I am a pro at this LOL. We lost TWO cars in one month to the CA emissions test (both cars ran ok too).
Oh yeah also, if your car fails horrendously, it can get flagged as a “gross polluter” and that will necessitate a test every year instead of every two years.
No wonder California is losing population…You reach a point, people just say "I’ve had enough of this…
“The test-only stations are more difficult to pass.”
I don’t believe this is true. I think the test only stations are the ones they send the older cars so that they reduce the conflict of interest between the shop that is doing the test and the one that is doing the repairs. If testing and repair are done in the same shop then there is a higher possibility that they will overdo repairs and charge extra. BUT I am sure the smog results needed to pass are the same in test only and regular smog shops.
@Caddyman I certainly felt that frustration! However, after complaining about it with some relatives who grew up in the LA basin in the 60s and 70s, their explanation left me glad we have the tests even if it meant losing my car (R.I.P. “Mighty MOfo”). CA’s population density and # of cars on the road necessitate it. They said in the 60s and 70s there were times the smog was like thick fog and days when you were told to stay inside and shut the windows. My uncle said if you took a deep breath you would start coughing. But yes, I know they also didn’t have cats then.
@galant You are correct, I just now checked up on that. And that’s a very good point. After my numerous fails, the tech would always say “We don’t do repairs, we can only refer you to someone.” In my experience though, when we took our car to our independent mechanic, he would be able to get an otherwise unpassable car to pass, so I thought the test only was more rigorous (regarding the CEL, not the emissions part).
A mechanic at a test only center told me that the test only stations were harder to pass and referred to the CEL. I thought he meant you could have the CEL on for the regular test station but I might be wrong about that. I expected the emissions standards were the same but I thought the other two parts of the tests were conducted differently. Perhaps he was only referring to that sort of loophole I exploited with my mechanic.
Not enough cars fail to make any difference, even in California…As you have discovered, they can be made to pass the test but is their exhaust any cleaner a week later?? Is the improvement, if any, big enough to make any difference in California’s air quality?
It’s a jobs program for the shops that do the tests and the government employees that pretend to supervise them…
Mousse, you uncle was not exaggerating. I remember seeing LA browned-out back in '71 when we flew there on KC135’s on our way to ferry fighters home from Viet Nam.