Check engine light goes off and on. Need to worry?

[Koolau]

How is that different from not having the codes?


If you are going to say "Why fix something if you can't detect any problem with the performance of the car?", there is a simple answer - "The Environment".


-ERD50

I agree that the environment is important. Having said that, I faced several hundred dollars worth of diagnostic tests and possibly hundreds more in fixing whatever was actually "wrong" with no guarantee that I would be helping the environment. Heck, there was no guarantee that ANYTHING was wrong. I know when a car is not functioning properly (gas mileage drops, it "smells" like poorly burned fuel, I can smell raw fuel, it bucks, backfires, hesitates, etc.) My car had none of these issues. Wild guess - it was the computer giving a bad diagnostic.

Before I would have invested big money in chasing a possible spook, I would have considered going to a shop which could check my emissions. I honestly didn't think I needed that or I would have done it. I guess we all have our priorities in this life. Perhaps others would have been more concerned than I was. When I go to my final reward, maybe I'll be "dinged" for this indiscretion - and maybe not.

As always, YMMV.

 

[wolf]

That is why you need a good mechanic. Or if you are a DIY, every Make/model car has a
forum (on the internet) now days. Just be sure and find the "good" one!

Cars seem to have the "same" problem(s) as they age. So when the "code" is given.
The mechanic, or "forum" members, usually know what is the most "common" fault.
This cuts down significantly the time it takes to fix the problem.

Been doing this for years, I'm on Honda Odyssey forum (2001 year of car), Toyota Camry forum (2002), and
Subaru Forester forum (2019). Also, check out you tube.

Good luck.

 

[ERD50]

I agree that the environment is important. Having said that, I faced several hundred dollars worth of diagnostic tests and possibly hundreds more in fixing whatever was actually "wrong" with no guarantee that I would be helping the environment. Heck, there was no guarantee that ANYTHING was wrong. I know when a car is not functioning properly (gas mileage drops, it "smells" like poorly burned fuel, I can smell raw fuel, it bucks, backfires, hesitates, etc.) My car had none of these issues. Wild guess - it was the computer giving a bad diagnostic.

Before I would have invested big money in chasing a possible spook, I would have considered going to a shop which could check my emissions. I honestly didn't think I needed that or I would have done it. I guess we all have our priorities in this life. Perhaps others would have been more concerned than I was. When I go to my final reward, maybe I'll be "dinged" for this indiscretion - and maybe not.

As always, YMMV.

Not true at all. Your emissions can be through the roof, and you would not notice any performance issues or smells. Remember, emissions are ~ 1/1000 what they were, there is a delicate balance to keep everything in line.

Are there shops that do a true "sniff the tail-pipe" emissions check anymore? Our State just verifies there are no bad codes, which is a pretty effective validation. So much stuff is checked, it all pretty much needs to be in order to pass everything.

I had a misfire code coming up on my Volvo (16 years ago!). I could never detect it, and I listened carefully. It was due for a plug change, I did that (easy-peasy on a 4 cyl FWD), and the light stayed off. Never could sense a thing.

-ERD50

 

[jimandthom]

Had a very similar problem with an 87 Accord Hatchback--- great car by the way.

Talked to our long-term mechanic(30+years) His response was to reinstall the gas cap as a starting point then bring it in so he could check things. That did it. Occured again later on, he ordered a new cap and never had another problem. Something to do with system pressure.

Finally got rid of the car in 2005/6. Exterior was rusty, but it ran great and the interior was still amazingly intact.

 

[Ronstar]

Otherwise, just give it time. It''ll let you know eventually.

DW's 2001 Acura had the check engine light come on in about 2010 when it had about 150k miles on it. Never had it checked. I drove it from Illinois to Arizona in 2013 and the light went off along the way. Went on and off for a few years. Drove the car back to Illinois in 2017. Light stayed on until I sold it in April of this year. Told the buyer about it and he didn't seem too concerned. Never did find out why the light was on.

 

[Mr._Graybeard]

The fuel tank vapor recovery system is probably the No. 1 source of trouble codes on OBD2 (1996 and later) cars. The fuel system is supposed to be 100% airtight, so when the computer runs its regular test of the system, it should be able to pull and hold a vacuum. Over time, the gasket on the gas cap can get brittle, or one of the many vacuum hoses in the system can lose their seal. That's when a 0440 code pops up. Generally the code doesn't show until the computer's second vacuum test fails.

The trouble code is so common, some makers have engineered a "loose gas cap" warning into the system. My 2005 Ford Ranger has one.

 

[Koolau]

Not true at all. Your emissions can be through the roof, and you would not notice any performance issues or smells. Remember, emissions are ~ 1/1000 what they were, there is a delicate balance to keep everything in line.

Are there shops that do a true "sniff the tail-pipe" emissions check anymore? Our State just verifies there are no bad codes, which is a pretty effective validation. So much stuff is checked, it all pretty much needs to be in order to pass everything.

I had a misfire code coming up on my Volvo (16 years ago!). I could never detect it, and I listened carefully. It was due for a plug change, I did that (easy-peasy on a 4 cyl FWD), and the light stayed off. Never could sense a thing.

-ERD50

Fine. How many years in purgatory do you think I'll get?

 

[ERD50]

Fine. How many years in purgatory do you think I'll get?

I'm not trying to be judgemental, I'm just explaining the facts. Not noticing a problem with performance does not mean the car isn't polluting far more than normal.

-ERD50

 

[CRLLS]

I don't like running with CEL "on", even if I know it is a fault that does not affect drivability or reliability. My issue with that is I will never know when a more serious issue arises.

A CEL being "on" is an immediate "fail" for my state's mandatory bi-annual emission test.

 

[ncbill]

CEL are usually emissions-related.

One of my older vehicles (~200,000 miles) threw a CEL.

Fixed it by adding a spacer on the downstream O2 sensor...no way was I going to pay for a new OEM catalytic converter on a vehicle that old.

 

[CRLLS]

CEL's can set by just about anything. I have seen wheel speed sensor, Input and output transmission shaft sensors, ABS system failures have caused my CEL to come on. Yes, emission related issues an cause a CEL but so can other things.

 

[ERD50]

I don't like running with CEL "on", even if I know it is a fault that does not affect drivability or reliability. My issue with that is I will never know when a more serious issue arises.

A CEL being "on" is an immediate "fail" for my state's mandatory bi-annual emission test.

+1

That's another reason it's good to have one of those $15 Bluetooth OBDII readers, that and a free app will give you detail on any/all codes.

And this isn't a theoretical problem, I actually had an issue like this in my old Volvo. Very occasionally, the CEL would come on, I read the code, had something to do with valve timing. But the internet told me it was a somewhat common 'problem', and had to do with a sensor very temporarily giving a bad reading during start-up until oil pressure came up. The advice, which seemed well reasoned with plenty of background info, not just "do this", was to just reset it, and see if it came back. And of course, you wanted to reset it, so that this code didn't hide another code that might pop up. They explained that the transient bad reading didn't really affect operation of anything, it was warning that there could be a problem, so the code was 'latched' until it was investigated.

And in my case, it came on maybe 1-3 times a year, for a few years, and then stopped. Never had to do anything with it, other than reset it. So maybe that's a downside, but pretty minor, and worth the far cleaner air we get.

-ERD50