The first time I took our '12 VC 70 to a touchless car wash, the washer spray blew the fuel door off the car.

There is a black inner door and a body color outer door.

It was easy to snap the outer door back on - I had to position the outer door near its location and push it in and toward the hinge.

If your car is like mine - try to push the outer door toward the rear of the car and pry SLIGHTLY out on the rear of the door.

OR - go to a touchless car wash and cross your fingers ;)

If you can get the outer door off - you MIGHT be able to jimmy the inner door.

Will a 1/4 of a tank get you to a dealer?

Perhaps someone with a model year closer to yours than mine could look at their mechanism.

From a Google search on - Unlock Volvo XC 70 Gas door -

- The XC70 MY2003 Manual says "NOTE: If the fuel filler door does not unlock after the button has been pressed, drive the car at a speed of at least 5 mph (8 km/h), stop the car, and press the button again."

- Had the same problem. Follow the instructions in the manual to the letter. Drive 5 miles per hour, no more, stop and then press the button. You will see Fuel Door unlocked in the left display and it will be unlocked. It does work. -Dick

I did npt read them all - there a LOT of threads to read.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '72 Yamaha Rd400, '68 Honda 350-4, '12 XC70, the first 5 are mine, heh, heh, 525,000 miles put on 10 bricks James A Sousa