NO BRAKE LIGHTS on my 2013 XC90 R design but i DO have the upper center light working, but it DOES have a few lights out. So i swapped it with the one off my 2009 XC90 (not an R design) just to see if it would make the regular brake lights come on butit didn't, and the 2009 center brake light worked on the 2013. So....i'm also reading on the forum that the center brake light and the regular brake lights are all connected. So nothing there either. Checked ALL FUSES IN ALL LOCATIONS, RELAYS and BULBS. Nothing. Main question...IS there a brake light relay for brake lights on the 13 XC90 R? I see on this forum YES & NO. Which is it? Getting really p'd off tryig to find solution and can't drive car til fixed! No, i don't believe it's the brake switch, I still can use cruise control. I would not be able to use cruise if it was faulty. PLEASE if ANYONE can help i would greatly appreciate. Been over a weekn ow with no wheelsl. VOLVO dealer wants 300+ JUST TO DIAGOSE!

 

There's one fuse (f9 on the CEM) for brake lights. If the center brake light works - the fuse is good.
No replaceable relay shown on the wiring diagram, but there certainly could be one soldered in the REM.
If the center light works, the brake light switch is ok

Do you have 12v (tested with your $8 test light) at the (two) yellow wires on terminal B3 on the REM, obviously when the brake pedal is depressed? (that go directly to the the left and right brake light bulbs)
If not you might have a problem in your REM. The first step would be to scan all the control units in the car with a compatible scanner. On some cars for instance if a bulb shorts to ground the controlling module will shut power off to that circuit (like a circuit breaker) until the short is fixed and the stored code is erased.
If needed a company such as xemodex can fix your REM

You can find wiring diagrams at volvodiag.com

 

We took out the brake light switch and put in another volvo and it worked fine. So i assume that rules out the brake light switch?