I have a 2001 Volvo V40 with 3000 miles and I'm currently experiencing this problem too. I made a call into the dealer just to make sure... However, reading all the responses to this post, it doesn't seem very serious at all -- more annoying than anything.

BTW, what's the worst case scenario if there's a fault in the emissions system? Could the engine be severly damaged?

As you can see, cars aren't my thing... Thanks in advance.

My check engine light also came on with my last fill up. I am 100% confident that it had nothing to do with the gas cap. I had left the key in the ignition, but it was set to position 1. That should not have caused it either. I had taken my tank down to refilling 13.2 gal. Not exactly dry either. Go figure. My Volvo service advisor assumed it was the cap. Not! Told me it would reset after approx. 30 restarts. It reset is less than 10.

The S/V 40 has a check in a fuel vapor line that does not have a return spring. It depends on gravity to close. Problem is the hose and valve are mounted horizontally and last i checked, gravity don't work sideways. There is a repair procedure outlined in a master tech manual that the dealer should have. It consists of repositioning the hose and valve to a vertical position to correct the false gas cap code. This applys to S/V 40 ONLY.

I used to get the reoccuring check engine light as well... it would come and go with no noticable cause. Luckily my dealer did not automatically blame it on the gas cap problem. They did say that what ever was causing the light it was not stored in memory (is the gas cap error even stored?). The only way I got to the problem, was one day I took it to the dealer the very moment it went on (I even left the engine running in the bay while i waited for a tech). Well, as some of you might know, all I needed was ANOTHER software download... I have had a total of about 4 on this car for four separate computers. Each time the problem has been solved. No more check engine light for me. I wonder why the dealer just dosen't check all of a persons software for the current version.

Andrew

2000 Red V40

Austin, Tx

I also remember reading somewhere that using 87 octane fuel can cause the same problem. I had what appears to be that problem at about 2000km. Of course the dealer blamed it on the gas cap, but I know it wasn't. I WAS using "cheap" fuel. Since then, I've used only 91 oct & have not seen the problem since.

It seems that the gas cap error is just a generic error code given when something goes out of specs, so the sensors flags the ECU for the check engine light! You said, your X40 was on a incline. First was your gas low? This can cause a check engine light to come on, something to do with the amount of fumes & gas in the tank or purge tank. I try and never get under 1/4 tank now :) I hate it when I get the check engine light, dealer said it was gas cap! Yea right. Remember that an X40 needs something like 6+ gallons to start up if run dry. Knowing this tells me that the fuel system is very sensitive too how much gas is in the tank.