My car's "Check Engine" light came on.

This happened last year around this time, it was a false alarm on the "fuel filler cap left open" thing. I hadn't left the filler cap off, but that's the code that came up. I asked the mechanic to look at it while I had the car in for something else, so he just cleared it and sent me on my way.

Since right now, the only thing wrong with my car is the check engine light, I would not be getting any value by taking it to the mechanic. The guy on the phone said it was a minimum of $78.00 just to plug the thing into his computer.

If it really is another false alarm on the fuel filler cap sensor, I don't want to spend 80 bucks every time this happens. I know I could just use the Click and Clack Handy-Dandy Black Tape (TM) but I also want to be sure it's not something more serious.

So now I want to get a device that I can plug into the car myself and read/clear the codes. There has been plenty of discussion on this topic with regard to building the feature into the empeg, but I'm just looking for a quick, cheap, off-the-shelf solution, preferably something I can interface with my PC to make it cheap as possible.

Anyone have any experience with these kinds of things? Suggestions?

For a 2000 Honda Accord?

Correct. Sorry, didn't specify.

I have heard that AutoZone (not sure if they have locations in CA) do free OBD-II scanning.

There's an AutoZone down the street from me. I'll check, thanks!

Brad, you may have just saved me 80 bucks. You are right, they do it for free, on a walk in basis. I'm taking my lunch now and going to do it. THANK YOU!!!!!

For all the help you've given me over the last year and a half, I still owe YOU!

PS - You mentioned that your last CEL was due to a gas cap. The cap doesn't need to be off, it just has to be loose. Any loss of vacuum will throw a CEL (I think it is emissions related). Usually, if the car can start 3 times successfully without a fault, the CEL will go away.

Heh, you -DID- save me 80 bucks!

The AutoZone guy didn't have the necessary book to look up the code, but a quick google revealed:

P1456 90 Evaporative Emission Control System Leak detected (Fuel Tank System).

Another gas cap false alarm, same as last spring.

Now I know that I should take it into the dealership and have it looked at under warranty. Emissions control systems, even false alarms, are covered by law for I think 5 years or so.

The cap doesn't need to be off, it just has to be loose. Any loss of vacuum will throw a CEL

I'm aware of that, it's even printed on the gas cap. I always tighten the cap securely, more than the "3 clicks" printed on the gas cap. I think that thermal expansion/contraction is making the sensor false-alarm. That is a characteristic of this time of year, cold evenings and hot days.

Usually, if the car can start 3 times successfully without a fault, the CEL will go away.

This does not appear to be the case with my car, as I procrastinated at least a week before posting anything about this.

Okay, let's make a couple of assumptions here. I'm just thinking out loud, so somebody stop me if I'm wrong...

Let's assume for a moment that there's not really a leak in my fuel system. Reasonable assumption, as I can go most of the year without tripping this pressure sensor.

Let's assume that I actually do tighten my gas cap and I haven't left it off.

Let's assume that it's really thermal expansion and contraction that tricks the gas tank pressure sensor into giving a false alarm. For example, the sensor is too sensitive.

Well, if the above is true, then there's nothing the Honda dealership can do about it because the parts are all performing within spec. I could go to lots of trouble to take the car to a Honda dealership and be without the car for a day, and all the hassle, etc., only to have them tell me, "there's nothing wrong with the car that we can find. You must not have tightened your gas cap".

So I'm doomed to have my Check Engine light go off at least once a year.

Does that sound like a reasonable series of assumptions?

If so, does anyone know if the tank pressure sensor can be defeated, and if so, would there be any other harmful effects of doing so (other than its inability to detect a real leak if one happens)?

Find it and cut it out.

Given that it is part of the "Emission Control System" tampering with it would be a big no no in legal terms.

Granted it is not as if you are removing the cat, but they won't see it that way.

So I'm doomed to have my Check Engine light go off at least once a year.

Does that sound like a reasonable series of assumptions?

Yes it does. Welcome to the wonderful world of OBD II. We see a large rash of the same problem in the beginning of the summer.

If so, does anyone know if the tank pressure sensor can be defeated, and if so, would there be any other harmful effects of doing so (other than its inability to detect a real leak if one happens)?

Aside from the possibility of it being illegal (probably is, don't know for sure), you'll be screwed warranty wise if your emissions fails. Not sure if it will hurt anything mechanically.

Thanks, glad to know it's not just me.

Okay, well, we'll see how the OBD2 project for the Empeg does. Maybe we'll have the product by the time my sensor trips again.

Hack your car with your laptop. here

Alright Im not sure if the new accords are like this but you should be able to check what code the engine is throwing yourself. Somewhere under the passnger glove box should be a little connector that looks like it goes to night probablt blue in color and has a two connection holes http://www.team-integra.net/sections/articles/images/connector1.jpg this is what you are looking for this do this http://www.team-integra.net/sections/articles/images/connector2.jpg . You want to do this with the car off. Now start the car with the paper clip completing the circuit you should see the CEL do a series of flashes. Long flashs are the first digit and short are the second. ie LONG SHORT SHORT is a code 12 EGR System Problem.

Assuming I can find this connector, is there a table of the CEL blink codes? The code I got from the OBD2 computer was a letter followed by four digits. Also, is it possible to clear the code from this method?

to my knowledge you clear the codes by removing power from the comuter (take the negative battery terminal off for a couple of seconds)

Actually to be safe do it for a 30 minutes. Then replace the cable to the battery. Start up the car and let it idle for about 10 minutes. Don't hit the gas pedal during this time. This time allows your ECU to make new data based on how much air it sees coming into. Use this time to reset your radio stations and clock. After 10 minutes is up, turn the car off.