Yesterday I was installing a back up camera on my 2010 XC60 3.2, the only electrical I touched was the plugs to the the rear taillights. I cut backup light wire and spliced in the power wire to the back up cam.
When I tried the back up cam it didn't have enough power to engage the camera but the screen lights up when in reverse. While trying to find the problem I tried pulling power off the other side (passenger) backup light but that didn't help.
I then noticed I had no rear blinkers or back up lights. Front and mirror blinkers work, lower taillights work, brake lights work. When I started the backup light wire gave me over 12 volts, now I'm seeing about 3 volts.
I tried unplugging the CEM plug(over night) and disconnecting the battery (about an hour), these were both solutions I found in the forums, but no luck with either, anyone have an idea?

 

With some Volvos - the CEM will shut power off to a light circuit if it detects a short. Like a circuit breaker. The only way to reset that "circuit breaker" is by erasing the code stored in the CEM (or the module that supplies power to the lights that are out).

So - the first step would be a scan with a compatible scan tool - looking for codes related to your reverse lights and turn signals.

Or - looking at the wiring diagram The reverse lights have a relay and a fuse on the CEM. Have you checked Fuse 11 on the CEM? Fuse 11 A/2 is under the hood and at 40A powers a whole bunch of stuff. Wiring diagrams available at volvodiag.com.