I've been getting an intermittent alert of Power System Service Urgent in my S80. It has usually happens when the car has been running for over 30 minutes and can last from a few seconds to 15 minutes. But it never stays. Just blinks on and then blinks off - sometimes a dozen times in a drive. The car doesn't seem to have any problems running. No changes noted in performance or charging. I replaced the battery and the cables are in good shape. I've had 2 different shops test the battery and alternator with normal results for both. Neither shop was able to recreate the alert code or diagnose any OBD codes that would generate such an alert.

The only other electrical issue with the car is that the radio will periodically go out and then come back on randomly. But there is no correlation with the alert.

Any suggestions?