Audi a6 central locking problem. Both of rear doors doesnt close. Has it got anything to do with the comfort module which controls central locking ?

If all else fails you may need to change the central lock system control module. You need to supply dealer with Vin #

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Does the motor turn over? If not is the battery dead? if not it could be your starter. I dont think its your central locking module. My understanding of it is that it runs your personal controls in the vehicle cab (windows, seats, radio ect) not the motor componeants

Check wire harness between driver door and body for broken wires.Wire harness bends , when door opens and closes so it may brake the wire or two inside harness.

More than likely your front driver door module has failed.  You will need to replace this module and readapt the key fobs for locking and unlocking

try squirting a lubricant lke crc or similiar in lock mechanism and dribble down button to lubricate, you may have to take door facia off to get the right spots i would try this first

I just saw your posting. Yes, It could be a fuse, a 10amp interior light fuse BUT... I had to replace the Central Locking Control module which toasted first... I had the 3 open door, no working lights/windows situation too...

The problem seems to be in the main cabin light which has the 3 way rocker switch. Turn this off (depress the side on the driver side of the car (US)). Check the 10 amp fuse for the interior light. If it is burnt, you are OK if its not, you need to replace the Central Locking module. ~$200 US

I still have not replaced the cabin light module where I think a short is. If I replace the fuse in question, and turn the cabin light on, it "pulses" for a few minutes and then cooks the fuse.

check that the plug is in properly and you havent pulled the wires getting the connector off ,and try that if it still doesnt work then its dealer only because i seem to remember that about this year vehicle doesnt have wires as such but bus lines and a module ,if it has then its dealer only because you have upset the module and it need to be re programmed back on line .encrypted software so its dealer only and no silly snap on reader .sorry for the bad news

1.  Check your owner's manual.  I'm not sure if it's the same as in my 2001 A6 4.2, but there should be a pin you can pull in the trunk that will disable the lock mechanism in your fuel door.  In my 2001, there was a red loop you pull in the right rear of the trunk, behind the cover panel.  My owner's manual references this pin in case of central locking failure.  You may need to dig around behind the subwoofer to find it.

As far as the central locking issue, it sounds like you need to replace your central locking pump. You can buy them online.
I have a 95 A6 and I am in the process of looking for a new central locking pump.
The part number may be 4A0 862 257 J, that is what it is for me.
There are directions online as to how to change this yourself once you get the part. If you buy from the dealership the part is $500.
Be thankful your child locks weren't engaged. We haven't been able to open our back doors since the pump went out.

If the A6 layout for the modules is the same as my A4, the lock pump is in the rear corner of the car, on the passenger side. In the trunk, pull up the carpeting behind the passenger rear wheel, and tucked down in there is the pump assembly. They're known to go bad and it's a pretty likely cause for your problem, provided your fuses are not blown.