My 2006 XC70 started having this problem about three years ago, a repair shop replaced the Fuel Pressure Regular but did not help. After I put fuel injector cleaner, and ran a couple of hundred highway mileage, the problem went away although it still could occasionally come and go. But recently, the CEL stays even if after I put Fuel Injector Cleaner and empty a full tank. The car drives fine and does not have any problem with starting, accelerating, and idling. What might be the root cause? Should I worry about it? Thanks a lot in advance!

 

BTW the idle engine pressure is 53.5 psi according to my coder reader.

 

Just noticed the Check engine light was gone...maybe the injector cleaner helped.