Brandon04GT

Hey guys, I posted this up on Honda-tech.com but didn't get too many replies so maybe people here can chime in also:

I got a 98 Civic LX, 4 door, auto trans, 135k miles. It's completely stock and I bought it about 18 months ago. The last time it was smogged was when I purchased it and it passed just fine.

Around summer or fall of last year, my car threw a CEL code. I had it read and it came out showing P0240 with the description something to the effect of "Catalytic converter running below efficiency threshold." I wasn't sure if it was just a random glitch so I had the mechanic just turn it off for me and it remained off for the next several months.

Then around the start of this year, it threw the same code again but this time I left the light on. The CEL remained on for about a week and then turned off by itself. It has since never come back on.

My registration is coming up and this time I need to get it smogged again. I'm worried that my cats might be bad, but i'm also wondering if maybe the P0240 code was just a false alert perhaps my sensors were dirty for a moment and then cleaned up by some extended freeway driving.

I know failing smog aint the end of the world but I would rather fix the issue beforehand and not have a failed smog check on the record if I knew I would 100% fail smog.

My question is whether there is a decent chance I can still pass smog or is a previous P0240 code a guaranteed dedication that my cats are bad?

If it matters, I am in CA and I haven't noticed any colored smoke or bad smelling fumes from the exhaust.


Thanks!

Gunner

More things could have contributed to that code other than the CAT.. your sensors could be bad, or the wire could be loose, or there could be an exhaust leak.. the code does not mean you will automatically fail.. you would have to test your sensors, and inspect your exhaust to isolate the problem.

ezone

I assume your local test only cares if the CEL is on or not for the testing?

Cat code is P0420, not 240.

Cat could be borderline, or maybe you got a tank of crappy fuel and the computer didn't like it.

CEL is out now? Been out for 2 months now?
As long as the light is off, you are probably OK to test.

Get a code reader that can display the emissions monitor OBD status so you know if it will fail or not before you go to test. (Don't bother to test if you know it will fail, duh.)

I'd probably try to get by on the original cat for as long as I could.
Fixing it right isn't cheap.

Brandon04GT

Thanks for the replies. I'm in CA so they do the whole dyno/tailpipe sniffer testing thing and I believe a CEL is an automatic fail.

The CEL is NOT on right now and has not been on for the last month or so. The last time it came on was sometime in January, and it stayed on for about a week then turned off by itself.

I have a habit of never filling my gas tank all the way which means I end up frequenting gas stations often and I've always used Chevron.

I'm wondering if the fact that it turned off by itself is indicative of anything?

Could you please elaborate on this a bit more? Do you mean I can go to an auto shop and find a code reader that can be hooked up to my car while the engine is running and it can give some kind of sign as to whether or not I have a chance of passing/failing?


Thanks

ezone

That's why I said "borderline".

There are other things that might cause a false cat code to set, like exhaust manifold leaks.

Get it tested while the light is OFF.
The cat test that the PCM runs has to fail twice in a row before the CEL turns on.

If it fails once, there is a "pending" or temporary code set, that stays until the next drive cycle self test run by the PCM. If it fails the second test during the next drive cycle, the CEL comes on, code is set and stored.


If the self tests run and pass 3 times in a row, the CEL turns itself off. Codes may stay in the memory much longer than that though.



I can see much value in knowing ahead of time if the car is definitely not going to pass an emissions test due to something stored in the computer that you can't otherwise see. (All you have otherwise is the CEL on the dash, right?)
You can figure this out by checking for codes and checking the OBD monitor status immediately prior to test time.

If nothing unusual is found stored in the computer, then you should be ok to do the tests. (If the cat is good enough to make the computer happy, the tailpipe sniffer test should pass easily. The cars computer is calibrated to be much more stringent than the sniffer, at least for certain gases.
(NOTE: I don't deal with emissions testing where I live. We don't have it.)



The more you know......

Brandon04GT

Alright thanks. So just to make sure I understand you, since my CEL turned off by itself, the chances are the car did a self test and it passed 3 times in a row, which is what prompted the turn-off.

However, the code may still be active WITHOUT the CEL on? So since I have no CEL on right now, is there something particular I am supposed to ask an auto shop to do when I drive to one and ask if they can use their reader to read my car?

In other words, should I ask them to check for a code even though no CEL is currently on? And also check for the "OBD monitor status"?


I appreciate all the help...hopefully I can pass then that way I won't have to worry about this for the next two years. And by then, I may have a different car.


Also, this is not really pertinent, but do smaller engines typically have a better chance of passing smog than bigger engines? Just kinda wondering if the emissions limits are the same for all cars regardless of engine size.

ezone

That's not just any chance, that's the actual reason the light turned off by itself.

You didn't erase the code, you didn't disconnect the battery, and you didn't have someone else erase the code. Right?

It's not "active", but it can be stored for much longer after the light goes out.

A customer might roll in to the shop saying the check engine light came on Friday night, but sometime during the weekend it went out by itself before they could get it in on Monday. In most cases, I can still see what the code was.

But not always. Depends on the code, the programming and criteria for that code, the manufacturer, and how the car was driven. Some codes might disappear immediately, some might take 40 drive cycles or some such. (I've seen so many variations over the years, I can't keep them straight. I have to look up info for each case.)
You can get a code reader of your own pretty cheap from many places.
IDK if Ca. allows parts stores to use code readers (I don't think so), or if they are allowed to let you use theirs. Parts stores are free to read codes here, erase your codes, and sell you a crapton of worthless parts to try to fix your code.

I wasn't advocating you using a shop for this. Any decent shop wants money for services of any kind.

I know if some Schmo off the street asks to "borrow" any of my scanners, I'm telling them to pound sand, GTFO of the shop.
That's is what the emissions test place will be checking for, so that's what I would be checking for. (I want to make sure I'm not wasting my time going for a test if it obviously can't pass.)

HOW you get it checked is up to you.
I'm trying to save you a pile of cash. If you can pass without replacing an expensive cat, do it.
If you buy a $50 code reader so you be more sure you pass the test without having to buy a cat, is that worth it? (You can still use the reader on your next car, and your friends' cars.)

No. Irrelevant, really. Any engine that runs well has a far better chance of passing than one that runs poorly.

Plus they may check stuff other than just the tailpipe or check engine light.
No. Limits may vary by years, engine sizes, emission controls equipped, GVW, your local area, federal regs, and much more.
Also, it depends on the testing types done.

My area does not have smog tests of any kind, so I don't have to deal with it.


JMHO. YMMV.

Brandon04GT

The first time my CEL came on was about a year ago, and I had it read and it was a P0240 code. I had the place turn it off and it remained off for months. Then around this January, it came back on again and I had it read and it was the same P0240 code. This time I didn't have them turn it off and I drove with it in for about a week and then it suddenly shut off by itself and hasn't come on since. I never disconnected the battery or anything like that.

Well most of the auto parts stores here don't offer a code reading service anymore but lots of "mom and pop" type mechanics offer to read codes for free (that is where I went to have the CEL read both times).

So I don't mean to keep going back and forth, but are you saying that even though the CEL is off now, I could go get a smog next week and the smog shop will plug his/her computer into my OBD port and it could say something to the effect of "CEL had come on in January, P0420," and that alone may lead me to fail smog?

If so, you're saying I should get hold of a reader to find out whether the previous code is still embedded in the history, and if so, either wait for it to go away and/or erase it?

Then, with no CEL on anymore, and no record of the code having been thrown (seen by plugging into the OBD port), I stand a decent chance of passing the emissions test?

ezone

It's not that exact, but yeah something like that.

Even though the light went out by itself, it could take (example and wild guess) 40 good and passing drive cycles before the code clears from the memory. Each code and every manufacturer may use different criteria to do this, that's why I wrote "guess".


No clue. I don't know what the rules are for your smog check program. I'm assuming it could cause you to fail.


If it has been 2 months and the car is a daily driver and you have a decent commute, the memory is likely to have cleared by now.
But I can't tell you that for certain. The quickest way to know if that has been done done is to check. No guessing.

Erasing codes also resets the OBD monitors, so you would need to complete the drive cycles in order to reset the monitor status to DONE for all the monitors prior to the test. Depending on your circumstances and daily drive scenario, that might take a long time to get enough of the monitors to run in order to not get an immediate rejection on the test. (Guessing you can have up to 2 monitors not run and still be ok?)
Again, the quickest way to know if they are done is to check. No guessing.

For the plug-in part of the tests, yes.


Your whole reason for making this thread was to figure out if you could pass the test since you set a cat code 2 months ago, right?
Either find out for sure about what is in the computer, or take a blind guess and hope.

Brandon04GT

Alright, thanks for the help. I think I understand. Yep, the car is a daily driver and it is driven several times a day. I'll try to get hold of an OBD reader and see what it says.

Gunner

as much as i dont encourage the places... an autoparts store will usually read your codes for free...

ezone

He's in California. I thought the parts stores were not allowed to do that for you there.


The one time that a consumer protection law works for people like me in the automotive repair industry, as aggravating as it is....

Gunner

hmm.. Might be a good point.. I honestly have no idea if they are or not.. LOL. Good point tho

Gunner

So i checked and you are right(was there ever any doubt..no) but what you can do is go to the store, rent the scanner, scan it in the parking lot make note of code, clear it and return the scanner.. law says it has to be a certified tech or the owner.

Brandon04GT

I know they used to allow it. They didn't rent it out, but they would go out to your car and scan for the code. I know they don't do it anymore.

But you can go to a mom and pop mechanic and just ask politely and they should be able to help you out for free.