I hear about “check engine” lights coming on due to a gasoline cap not being peoperly closed.
What asshole of an engineer thought that was a good idea?
Since it cannot be reset (at least in some cars) except by a visit to the dealer, one has to waste a day to determine nothing is actually wrong with their engine.
A colleague suggested that a simple LED on the dash indicating open cap would suffice, and I agree wholeheartedly.
My dealer has a sign up that says resetting the check engine light due to a loose gas cap is not covered under warranty and will be henceforth be billed accordingly.
So what gives? Is this a scam to get people’s cars into the shops? Or was it just stupid design?
I dare someone from the Detroit brain-trust to defend this.
PS This didn’t happen to me, but it did happen to a family member!
I am not from the Detroit brain trust, but the rationale as I understand it is this.
If the gas cap is loose, then low pressure is detected in the fuel tank and the check engine light comes on. The reason this is a problem is because gas fumes leaking into the atmosphere is a bad thing. The majority of check engine light causes are emission related problems.
Although this has never happened to me, it is my understanding that if the gas cap is properly tightened, the check engine light should reset itself after some period of time although it may take days. I’m not sure if all cars will auto-reset the light though.
But the “Check Engine” light pretty much always indicates an emissions problem. It doesn’t indicate an “actual problem” in the sense that a breakdown is imminent.
A loose gas cap - and the attendant problem of evaporating fuel - is supposedly one of the nastier types of air pollution cars can create. I’d say it’s worth indicating.
The trouble is, there are already so many dashboard indicators. They cost money. By grouping a bunch of emissions problems together under “Check Engine,” the count can be kept a little more reasonable. Some high-end cars now use alphanumeric displays instead of a million different “dummy lights,” so they can say “Tighten Gas Cap” instead of “Check Engine.” More cars will probably use such displays in the future.
My SO’s car will light “Check Engine” for a loose gas cap, but the light goes out if the gas cap is tightened. I agree that requiring a trip to the dealer for this particular problem is pretty poor.
I find it amusing that th “Detroit brain-trust” is blamed, for this, while most all newer cars, made in Detroit, Japan, or Europe, use this same feature.
It’s not that big a deal. If your check engine light goes on, get your codes rad. Use your own OBDII code reader, or, if you don’t have one, which I’m sure you don’t, most auto parts stores will read them for you. Most will even suggest fixes. If not, the Internet is a wonderful thing. Too much trouble for you? Bemoaning all these “fancy-schmancy” cars? Well, back in the day, we didn’t have emissions controls, and that was not a Good Thing. How would you like today’s emissions controls with yesterday’s alert technology? In the old days, you’d have no clue that your gas cap was loose, you’d just pollute the environment, and get crappy gas mileage for that tank.
The solution, of course, is the be aware that a car is still a complex piece of machinery that requires active intervention from the user. Ignoring that is foolish.
BTW, my 2003 Detroit car has a message that tells me “Chck Gas Cap”.
Auto engineers (I’m not one) are limited by nudging from upstairs. Two big fat nudges are these:
If we can do this more cheaply, the stockholders get more money, and you won’t get fired.
If we can do this more simply, we’re less likely to screw up while building it, and it’s less likely to break in the field, and you won’t get fired.
Now, there might be a cheaper way for you to reset your Check Engine Light. Go to an auto parts store such as Auto Zone, and ask for advice. I’ve heard they have a very cheap doodad you can plug in under there. When you do that, something on the dash will flash a certain number of times. You match the number of flashes to a problem on the chart. The chart also tells you how to reset it.
Now, why didn’t this doodad come with your new car? See Nudge number One above. It would have cost a few cents more.
First off let’s get one thing straight here. Turning on the MIL is not a function of what Detroit (or Toyko, or Stuttgart or where ever) thought was a good idea.
This is your government in action. This is a legal requirement that if the evaporative emission system has a leak (current law is check down a hole of 0.5mm, IIRC) then the system must flag the fault.
I mean what good does it do to have computers, fuel injection, exhaust controls if Bubba is gonna leave his gas cap off and just pour hydrocarbons into the air. Having it this way does make sense if you look at it from this point of view.
Believe me speaking as a guy who teaches factory technicians all day every day, we don’t like it any more than you do. It causes extra work load for no good reason.
As far as charging for it goes, some dealers do and some don’t. After you see the same customer 4 times for a loose gas cap the arguement for charging is that this is a stupidity tax for anyone who is not smart enough to install a gas cap correctly.
I don’t mind that the Check Engine light comes on if the gas cap’s loose. It makes sense that the emissions regulations would require this. But why should it take a certain number of days, or starts, or any arbitrary condition other than simply fixing the problem to reset the light?
Shouldn’t it shut off if the problem goes away? I’d be pretty upset if, say I got an oil leak, the oil light goes on, and when I get it fixed the mechanic told me, “Yeah, the oil light will stay on until you start your car 50 times”.
Anyone care to defend this seemingly lax bit of engineering?
I had a problem with this. Some punks stole my gas cap and I did not realize that would cause the check engine light to come on. I took my car to the dealer to have it looked at. I told them the check engine light was on, and I also needed a new gas cap.
The bastards charged me $30 for a new gas cap, and “fixed” something else that ended up costing me $500.
Shortly after I just spent all that money to have my car “fixed”, the punks stole my gas cap AGAIN! The check engine light came on, so I looked in the manual and found out that a missing gas cap would trigger the light. I went to Pep Boys and bought a gas cap (w/ a lock) for around 10 bucks. I put it on, and the light went off.
Needless to say, I was pretty pissed about being charged 500 dollars for a repair that I did not need. bastards!
I can live with the loose cap lighting the Check Engine light.
I have problem with it not going off after it’s screwed on properly.
Hell, if any problem that illuminates the Check Engine light is fixed, the error should automatically be cleared; it should not have to be manually cleared by a technician!
Well, your car probably doesn’t have a dedicated “gas cap sensor” - that would be expensive. The engine control computer monitors the pressure in the gas tank, not the presence of a gas cap. With a sealed fuel system, the expectation is that the pressure in the tank will usually be below atmospheric. I can think of a few reasons for what feels like an arbitrary delay between the fix and the fault being cleared:
Your fuel system may actually only be marginally well-sealed, and it may be struggling to lower the pressure of the system.
The ECU can’t be too hasty to convert pressure data to leak/no-leak status, since the pressure can change suddenly (like at fill-ups) even when nothing is wrong. Some delay before diagnosing (or clearing) a fault indication is prudent.
It could be strongly influenced by driving conditions; if you top off the tank, carefully seal the gas cap, and immediately proceed to burn 1/2 a tank of gas by driving across the state, your fuel system may have no trouble getting the pressure down into the expected range very quickly. If you only buy $5 worth of gas at a time and make mostly short around-town trips, it may be more of a struggle, because the sudden evacuation of the gas tank isn’t happening, and because slow leaks have time to act.
For what it’s worth, my SO’s car, which has demonstrated this problem a couple of times, was able to clear the fault after less than an hour of driving with a tightened cap. So this type of system can work reasonably well.
But I’m no auto-tech maven. (Mavens: please correct and/or amend!)
I believe the rationale is that a fault could be intermittent, so the behavior is generally to flag the fault until someone can check the problem out. For example, if something hiccups and you briefly have the wrong mix of oxygen in your exhaust, the oxygen sensor faults and stays flagged until you take it to the shop and they determine whether it was a fluke, a faulty sensor, or an actual emissions problem.
Granted, some faults are easily explained to the user and easy for them to remedy, so it would make a whole lot of sense to allow these faults in particular to auto-reset without taking a trip to the dealer.
For my car, I bought a little tool for $130 or so that plugs into the diags port on my engine and tells me the fault code, giving me the option to reset it. If it’s the oxygen sensor or the gas cap or something minor, I’ll usually just reset the fault and see if it happens again. At the very least, it’s nice to be able to figure out if the fault is something I need to have addressed immediately, or if I can deal with when it’s convenient.
Well I guess I qualify as a maven, so let me chime in. Although I don’t think anyone has ever called me that before.
There are several system out there to detect leaks. Some use engine vacuum to check the system while driving, some use a pump to check while driving and some use a pump that checks when the key is off. Plus there are probably three or four other types/wrinkles of systems that I am unfamiliar with.
All of the systems that I am familiar with the system tests independently of any previous tests. So Lagged2Death suggestions about adding 5 gallons of gas, or the ECU being able to keep up really don’t apply.
What does have an effect is how the car is driven. On one type of fuel system the ECM checks for leaks 17 minutes after engine start and then only if the engine is at idle. This is great unless 17 minutes after engine start you are on the freeway going 70 MPH. if this occurs then system won’t test during this key cycle. How when the system tests, is left up to the engineers for the car. What can I say except some engineers are better than others, some design more end user friendly systems than others.
Based on what goes on with my own company I can say that the systems are getting more lenient and forgiving as they move through the generations. On our more recent cars, if you leave the gas cap off, a message will light up “check gas cap” The system will then retest the next time the car is shut off. If all is OK nothing further is done. If the fault still exists, a check engine light is then turned on. BwanaBob Yes OBDII allows in the case of an intermittent problem for the check engine light to get turned off with no intervention from a technician. However see my comments above about the quality of engineers and their work output. Also if the fault is permanent the light must stay on. Just because the light is on, it does not always mean a loose gas cap. On the car in my shop right now there are about 400 different things that are monitored by the ECM about 75% will set a check engine light.
Which brings me to ** horhay_achoa** You are making the assumption that the only problem with your car was the missing gas cap. Without seeing the paperwork, and technician notes, I cannot say for certain, but I am guessing that there was something else beyond a missing gas cap wrong with your car. From the information provided no can make a determination if the repairs to your car were justified.
