check engine light question

[atgcpaul]

I've got a 2010 Hyundai Santa Fe. I'm the original owner and it's still under warranty. My check engine light came on about a month ago but then went off a day or two later. I think after I filled up the gas. I do remember that when I initially opened the tank, the smell was much stronger than usual. I think the tank was below 1/4 when I filled it.

So a couple weeks pass and light comes on again. Gas is around 1/4 again. When I fill it, it goes away.

So today tank is 1/2 full and light comes on. So I fill it up (I tend to let it run low) and the light goes away.

It didn't start until the weather got really cold (for here). I've read the if you let the gas run too low, the water in the gas can freeze in the fuel filter and give you this problem. I've also read it shouldn't be as much a problem nowadays than it used to be. It's almost 50deg today so I can't imagine it's frozen.

Anyway, is it correct that the OBD reader is only going to help if the light is on--so I have to wait until it happens again?

Do you think this is going to qualify as a warranty item or routine maintenance? I have a mechanic I trust but if the fix is free then I'll take it to the dealer. I don't trust those guys at all. I think they take their best car sales people and put them in the service department.

Thanks,
Paul

[cork58]

Take it in for warranty work. The C.E.L. most always is an emission problem that is always on them under warranty. Sounds like an evap problem to me.

[LinuxRandal]

Several of the autoparts stores will plug in a reader and tell you what it says, for free. The issue I have with them, is some only use a code reader, verses the more equipped (and costly) diagnostics machine). This may however still tell you what you need to know (don't let them reset the light)
Even if the light isn't on, you system should show it as a history code.
It could be either warranty, or a maintenance issue. Changing oil, isn't warranty, nor would I think changing a fuel filter (unless in the gas tank/some Chrysler models), would be. (clogging filter would affect pressure) A fuel filter isn't the only cause (anyone else drive it?), as the garage I worked at, was the first place I saw the infamous loose fuel cap, error code. (dealer would charge for diagnosis and tightening the cap in a lot of cases)

If your suspecting water, or gas issues, it is fairly inexpensive to use either heet (not sure of the spelling of it) or Seafoam, to try to dry up the water in the tank.
Your system is OBDII for sure and that date (I've been out of it for a while), I am 85% sure is Canbus. (a lot more information then just emissions)

[durango dude]

Your dealer has an arrangement with the manufacturer ---- make the lights turn on every 30,000 miles or so ---- so they can charge you $100 to pull a code, and another $250 to replace at least one part. (joke)

Since it's under warranty ---- take it in!

I have a code puller ---- and yeah - most dummy lights I get are for the emission system.

Modern vehicles have all kinds of mechanisms to manage fumes. They do it through a set of vacuum hoses and carbon canisters.

Chances are, you have a filter that's due for a change, or a hose that's worn out/clogged.

If you get a code puller and a Chilton/Haynes manual - you can likely figure out the issue. There's even a decent chance you can fix it yourself (about a third of the issues modern cars will have require dealer mechanics, due to specialized equipment/procedures/parts --- one third can be done by your local mechanic --- one third can be done by you).

[mpc]

What the OP described sounds like an evaporative emission control system issue. In a nutshell: that system is supposed to capture gas fumes from the entire fuel system as gas tries to evaporate. The heart of the system is a charcoal canister that absorbs the fumes, basically similar to the "Odor Eaters" for your sneakers. When the engine is running and warmed up, a computer controlled solenoid opens to allow engine intake manifold vacuum to suck on this tank, drawing the trapped fumes out of the charcoal. The gas cap is actually part of this system too: as you use gas in the tank, air needs to get into the tank to make up the volume. Gas caps have a spring-loaded door in them; when enough gas has been removed from the tank to develop a bit of a vacuum the door this vacuum pops the door open for a moment allowing outside air into the tank. There are a few pressure sensors in the system as part of the OBD II requirements to make sure the system is functioning. One sensor measures the vacuum in the gas tank... the computer expects to slowly see that vacuum build up as you drive and then suddenly go back to zero when the gas cap opens. As long as the computer sees this cycling it can assume there are no leaks in the fuel tank, fuel pipes/hoses, and that the gas cap itself doesn't leak.

The computer monitors the magnitude of vacuum buildup. When the tank is nearly full, it doesn't take much fuel drawn into the engine to make significant vacuum. When the tank is only part-way full, there is a lot more air to start with... so it takes more engine operation to burn enough gas to actually build up significant vacuum. If your vehicle has a teeny leak in the hoses/gas cap/etc. then it'll make it that much harder to build tank vacuum when there is more air in the tank to start with...

Many "check engine" light problems are covered by the vehicle's emission warranty which is often longer than the basic engine warranty; on Hyundai's both are 10year/100,000 mile for the original owner. And OBD II "check engine" light codes are stored in the computer long after the light goes back off.

Recent Hyundais (and likely many other brands too) also have a "fuel tank air filter" that is supposed to be replaced at something like 30K or 35K miles. Many dealers don't like doing this job as part of the "30K service" because it takes a bit of time. If that filter gets gunked up, air can't get into some of the other evaporative emissions lines and the whole system performance suffers.

mpc

[cwsmith]

I have a similar problem with my Dodge Caravan... IF I let the gas run too low, the engine light comes on. I took it in to my service garage and the guys joked with me about "when was the last time you put gas in this thing?".

I was a bit embarrassed by my stupidity, but as mentioned a few times in the previous responses, I think it's all centered around the fuel system and the many sensors that are monitoring it. In my case, much had to do with the gas cap seal, and the fact that my fuel had dropped to below a qtr tank.

A sensor check (ODB?) at the garage couldn't find anything particular, but I did replace the gas cap, as the old one was the original and it just seemed to be quit loose. Since then (about four months now), I haven't had any indications. I do try to never let the tank go below a quarter tank though.

CWS

[TB Roye]

Now a day with the electric fuel pumps in the tank letting the gas get to low can cause the pump to get hot, not enough to cause a fire but driving low fuel consistently over time will possibly shorten it life cause it to fail the gas acts as a coolant for pump. Been told this by a number of dealer mechanics

[lrr]

Our Honda Pilot did that when we first got it. I bought a diagnostic tester and the code was for the emissions system. For the Honda, you tighten the cap "3 clicks" -- no more, no less. Any more or less, and it can register as a closed systems leakage. If the cap is bad, it would have continued. By tightening as directed, the light has never come back on.

Go check out one of the forums for your car, and post the question. It may be something simple like I discovered.

[greencat]

Does sound like an emissions problem. If you have a smartphone you can get a OBDII adapter for $15 or less. The regular code readers are over $100. The adapter is inexpensive because it uses your phone as the computer.

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[JimD]

I have a OBDII reader/reseter but what I normally use is a tablet/phone app called "Torque". You can try it for free or pay $5 to be legit. You also need a OBDII to bluetooth adapter. I paid about $25 for one from Amazon but there are cheaper ones. Torque not only lets you read and clear codes, it also allows you to monitor most sensors on the car. I believe it will also let you see stored codes - which you may have from the previous incidents. I've used torque to create vitual gauges for things like air to fuel ratio. It's fun to mess with but also very handy when you get a code. You get a short description of the code in the application and can then google it to get more.

I agree it sounds like a small leak in the evap system. A "smoke test" would be useful to have done, a decent mechanic can do it. All you do is waive a smoke pencil around the evap system looking for a leak. My 2006 Grand Vitara had a non functional evap pump when new and the smoke test found the issue (after several trips to the dealer).

Jim

[Stytooner]

Never reset the code! I am not sure how long it stays in memory, but I imagine different lengths of time for different vehcles.
I bought my 06 Dakota with 39000 miles on it. It came with full factory re certified documents. So, full warranty.
It has had and still has issues with the dummy lights.
At first, the check engine light indicated a cam sensor. They replaced it. Then a transmission sensor. They basically did a transmission service and charged me for it while replacing that sensor. That was $700.00. The F'ing light still comes on intermittent for trans temp. It does this generally when first leaving the driveway. I know the trans is not hot. They have it documented at the dealer.
If the trans does go out, I'll get me a discount.

It does pay to be a frequent flyer with my Dodge dealer.

[lrr]

[...]

It does pay to be a frequent flyer with my Dodge dealer.

Funny thing -- we have a 99 Dodge Grand Caravan, with a little over 100K miles, and it has been the most reliable vehicle we have ever owned. The planets must have been aligned when it was built.

I has had repairs like you'd expect, such as needing a new water pump at about 80K miles, but now it just seems to be suffering from old age. Splits in the leather, a screw coming loose from the air dam under the front bumper, etc. It was built in the Daimler-Chrysler days, and I wonder about new Chryslers now that they are a owned by Fiat ...although some of their new vehicles are getting pretty good reviews.

My Honda Pilot has 125K miles and runs great. And doesn't use a bit of oil between changes. I'd love to buy domestic the next time, and maybe consider a Ford Explorer for the next SUV, but I've been spoiled driving the Pilot.

[greencat]

Resting the code with a obd2 tool is OK. What is not Ok is resting the code by disconnecting the battery. When you remove the battery you lose a lot of good data.

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[atgcpaul]

Does sound like an emissions problem. If you have a smartphone you can get a OBDII adapter for $15 or less. The regular code readers are over $100. The adapter is inexpensive because it uses your phone as the computer.

Sent from my SCH-I545 using Tapatalk 2

Thanks for some of the great explanations on what could be happening.

I couldn't resist getting a new gadget. Bought a new one off eBay yesterday for $12.99 and free shipping. Should be here Friday. Hopefully the codes will be meaningful. And no, I have no plans on resetting them. I'd rather stick a piece of tape over the light

My gas cap only lets you get one click to close--also printed on the cap. One of the first times the light came on, I did open and close the tank. The light went away. I've tried it again on subsequent occasions but no joy.

The temps have warmed significantly and I'm almost at a quarter tank and no light. Just a few days ago I was at half and had the light but it was also below freezing then, too. Anyway, I'll try my best not to let it run low so I'll fill up before getting into work today. Friday can't come soon enough.

[JimD]

When you use an absolute (like "never") you are nearly always going to be wrong. I used to use that principle on multiple choice tests while in school (many years ago) and still use it for training today.

Resetting codes without knowing what they are isn't a great idea. It could be the silly evap system but it could be something that actually affects the cars performance. But some issues are OK to do a "wait and see" on. My daughters Corolla threw a code that was most likely to be a leak of the plastic intake manifold against the aluminum head with cold weather a possible cause. I reset it and it hasn't come back. Resetting the evap code when you're pretty sure it was the gas cap is fine. But if you plan to take the car in for service, it is best to just leave the code for the dealer to see. They should be able to find it even if you resett it but making it obvious isn't a bad idea.

So it depends on what the code is. You should read it, google it to understand likely causes, and then if you are sure the car is not in dire need of service, reset it.

Jim