Check engine light was on....now it's off!

Has happened to me at least 4 times since the car was new (2001 VDC). First two times I took it back to dealer and,both times, he allegedly replaced something I think he called a "sender"in the gas tank. Both times, though, he said no harm in driving car until he could take care of the fix ... a week or two. Last two times I said "nuts" and just continued driving, Problem eventually went away. Once, time before last, VDC Off light came on at about same time as Engine Light. Within a day that returned to normal and within a couple of days (fairly light local driving) engine light went off too.

In all cars, when the CEL light is on steady, it means that there is some sort of problem with the emissions. It is nothing serious, and you can continue driving the car. Many times, the condition clears up, and you are left with a mystery. Could be water or in the gas, blocked air intake, almost anything that would affect the emissions.If the light does not go out by the next service, have them take a look.

If the CEL is fLaShInG, that is usually serious, and you should take the car to the dealer immediately.

I wouldn't write off the gas cap just yet. Several months back I had a problem with CEL coming on the going off numerous times for almost a month. Finally took the cap off, cleaned off the filler neck real good to insure it was real smooth, next removed the rubber seal on the cap and cleaned it well. CEL hasn't been on since that time.

Mickey

Well, I would first find some place that would read the code for free, like autozone, or 76 gas stations since there's no autozone near me, to read the error code. If your CEL is on, there can be an error code stored in your Engine Control Unit computer, and reading it can let you know what the ECU "think" the problem is. If the light goes off then there's no code stored.

And yes a computer can always be fooled. There was once my CEL was on and the error code told me there was leak in a pipe, I found no leak and reset it. It never bothered me again.

Sam

What makes this out of warranty?

Engine and Powertrain mechanical

Just read this thread - my apologies if I am not replying in the correct manner....

But can somebody please explain the fuel cap / CEL relationship for me? I've never heard of this before. Is there sensors/wires in the filler neck that register emissions???

Thanx in Advance spinifex

Just read this thread - my apologies if I am not replying in the correct manner....

But can somebody please explain the fuel cap / CEL relationship for me? I've never heard of this before. Is there sensors/wires in the filler neck that register emissions???

Thanx in Advance spinifex

It's not exclusive to Subies anymore...in the quest to reduce emissions, raw fumes from evaporating gasoline are also considered pollution. I haven't done the "complete" analysis, but I'd guess there's an "air" line to the intake from the fuel tanks, that will put a slight vacuum in the tank headspace, to pull fumes into engine. There's a charcoal canister back there too, that absorbs fumes during periods of nonoperation, and should be in the draw-down loop, too.

All that puts a slight vacuum on the tank headspace, which includes the filler neck. If the gas cap is loose, the vacuum won't develop. A vac sensor in that area will notify ecu if the proper vacuum level is not achieved, and the ecu will store the corresponding error code, and flash that darn lil light.

Steve

There's an evaporative pressure sensor in modern fuel tanks to measure the vapor pressure in the tank above the fuel.

Too low a pressure, and your CEL will come on indicating either a gas cap seal failure, a hole in the tank, etc.

-- Todd H.

I wonder what the cost trade-off is for manufacturers to add a light that says "Check fuel system" instead of the CEL??? Or even a special flash sequence, or at least something more useful than the "something is wrong with this huge piece of equipment, but it's top secret and it'll cost you to learn what it is" light. :-)

-John O

I'm told AutoZone will tell ya for free with their ODBII reader.

-- Todd H.

Many of the codes are common regardless of mfgr. See the same description for code number on my Ford CV. This is very confusing when some codes mention bank 1 or bank 2. The bank info applies to engines with separate systems for left and right banks you might find in V6 and V8 engines.

On my car when the light came on the code was 420 which is a code for the cat system, bank 1.

For all the hundreds of codes, some are not very useful in understanding what is actually wrong.

Mickey

Thanks all for the good replies. The light remains off, and I'm still driving around, so keep your fingers crossed!