I am driving 2001 S60 2.4T with 96,000 miles. This warning light came on about two weeks ago and it went out two days later. It came back on again a week or so later and went out again. The next time, I took notice of all conditions and noticed that the light came on after I filled the gas. There is a warning on the refill cap door about fill gas while the engine is running and the associated warning light. So, the next time I fill I hit the cap a few times and screwed back in. The light did not appear. After a few miles the warning light came on again. I have an OBDII reader and I will read the code an reset it. Some sensor is reporting to the computer and I would like to know which.

 

What's the code you pulled with your OBD II scanner?

And how's the gasket on your gas cap? If the gasket is bad it will trigger an emissions CEL from having an evap leak. Just a thought since you mentioned the gas cap...
If it is an evap leak, this is your solution...
Fuel Filler Gas Cap Seal

 

Thank you. I havn't applied the OBDII reader yet. Will do it tomorrow. Will report when read.

 

Apologies for my late reply. I was getting my OBD II reader and lost some time. I got it yesterday and went for a drive. During this time, the service came on and went off. When I fitted the OBD II the light was off and therefore no error code was shown. After a few miles the light came on again and I reconnected and tried to read the error codes. There is no error code. After driving for some more miles, the light went out again. Today, it was on for a few miles and it went out again later. I could not make any conclusions from this.