I recently purchased a 2007 Audi A4. When I use the remote to lock and unlock the doors, the door to the fuel tank pops open. Any clue why?

seperate switch in door maybe or a push type system ,meaning when you push fuel cover it pops open

InInside the drivers door in the back of the storage compartment is the switch to open the fuel door.

Thanks for choosing FixYa and welcome. Try going through the trunk. There might be a cord or an access port that you may be able to find to get through. It should be on the same side as the gas tank port/gas cap. If your manual gas tank opener is not working, you might be able to get a hold of the cable and pull it. There is a cable that opens it.

Pull the trunk wall lining back by the fuel filler. On my 99 A4 there is a red cable there - it's an emergency release that will pop the gas door open.

I would start with driver door lock , not the lock cyllinder , but lock assembly which is inside the door and have switches build in to it.

Open the drivers door with the key. Look on the door for the unlock button and press it. This will unlock all doors and the boot. Use the handle on the boot to open it.

I recently picked up an 2001 Audi and the dealer told me that this is one of the most common questions. You have to double press the unlock button of your keyless entry pad to unlock all doors including the fuel access door. Perhaps you are checking the fuel access door while all doors are unlocked?

Open remote clean contacts w/alcohol get the correct battery--or go back to the owner -bull

Enter car from left rear behind the driver and see if you can manually unlock it from the inside. Then use remote to test it.

I have a 97 and there is no release for it. Just push on the right end of the gas cap door to open it. Hope that helps.