About a week ago my 2006 XC90 lit a message FUEL CAP LOOSE OR OPEN, I opened and closed the cap back but couple of days later it showed the same thing. After 3 same messages CHECK ENGINE light came on. Did not run the diagnostics yet but it just today showed the same message FUEL CAP LOOSE OR OPEN. Any advice? Thank you.

 

The gasket/O-ring may be bad. Check to see if it is drying out or cracked. If it is then just pick up a new one at Autozone, etc. That is probably what is causing you to get a CEL.

 

replaced the old cap with the new one from Volvo dealer, CHECK ENGINE light turned off but 3 days later came back on.... Any advise?

 

get the codes scanned by an OBDII reader (free at autozone). it may show something other than or in addition to fuel cap.

 

disconnected the battery for about 30 sec, reconnected it and that keeps the light off since