I think this question has been answered, but to add some specifics (at least to my case) I had this error message and replaced the bulb on the light on the rear bumper mounted on the curvature of the bumper itself (ie not the larger tail light). It seemed to do the job - poor description on the part...

I have an '04 XC90 AWD and wondered if anyone has any experience or opinion in terms of pushing the rated towing capacity on the vehicle. The manual states 4960 lbs max towing capacity. I'd like to tow a boat I just bought, but I figure fully loaded boat, motor, fuel, gear and trailer puts me closer...

I have a 2004 XC90 with 46k miles. I have had the rear wheel bearings replaced twice (once about a year ago and once a few weeks ago). Both times the dealer did the work under warranty; however, the dealer also did not know of a broader issue.