On my 2003 Avalanche, the power locks on both rear doors will not lock electrically. This began as an intermittent problem but now the only way to lock the rear doors is manually. Both rear doors will un-lock with key bob, door switches, and as programmed on steering wheel.

No not a fuse. You need the dealer to scan the body control computer, it may have failed.

Doesn't use a fuse , ues a circuit breaker . These very rarely go bad .The right rear door works ? Uses same circuit breaker as front passenger door. The power windows an locks on your vehicle are controlled by electronic control modules . FPDM - front passenger door module , I would look for a broken orange wire inside the flex boot from the body to the front right passenger door . This is power supply to the passenger door module . Do you know what wiring diagrams are ? Free here http://www.bbbind.com/free-tsb

As per this problem,there are help links provided to troubleshoot the exact cause of problem.Click the link below to go through the procedure :----Diagnosis & Testing Power Windows? http://repairhelpcenter.blogspot.in/2012/02/diagnosis-testing-power-windows.html----------
Door locks or windows not working on car?
http://schematicsdiagram.blogspot.com/2011/07/door-locks-or-windows-not-working-on.html
------------Car windows will go down but come right back up
http://schematicsdiagram.blogspot.com/2011/06/car-windows-will-go-down-but-come-right.html

Electric Window Motor REMOVAL and INSTALLATION ?
http://schematicsdiagram.blogspot.com/2011/06/electric-window-motor-removal-and.html
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Driver side power window wont go up on ford expedition?
http://howtobyme.blogspot.com/2011/10/driver-side-power-window-wont-go-up-on.html

How to replace window motor and regulator on jaguar S-Type?
http://howtobyme.blogspot.com/2011/09/how-to-replace-window-motor-and.html

How to remove window motor and regulator?
http://howtobyme.blogspot.com/2011/09/how-to-remove-window-motor-and.html
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power locks, power window and power mirror on the passenger side not working ?
http://howtobyme.blogspot.com/2011/09/power-locks-power-window-and-power.html
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All power windows not working?
http://howtobyme.blogspot.com/2011/09/all-power-windows-not-working-on-2003.html
-----------Power windows works intermittently? http://schematicsdiagram.blogspot.com/2011/12/power-windows-works-intermittently.html
--------Power window fuse location? http://schematicsdiagram.blogspot.com/2012/01/power-window-fuse-location-for.html
----------Power windows will not go up and relay clicks when switch is pressed? http://technoanswers.blogspot.com/2012/01/power-windows-will-not-go-up-and-relay.html
----------Keyless keypad on drivers door stopped working?

http://technoanswers.blogspot.com/2012/01/after-alternator-failure-keyless-keypad.html

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Remote will not unlock Rear door ?
http://schematicsdiagram.blogspot.com/2011/12/remote-will-not-unlock-rear-door-on-gmc.html
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Door locks or windows not working on car?
http://schematicsdiagram.blogspot.com/2011/07/door-locks-or-windows-not-working-on.html
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Car door will not close?
http://howtobyme.blogspot.com/2011/11/car-door-will-not-close.html

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All power door locks not working on?
http://howtobyme.blogspot.com/2011/11/all-power-door-locks-not-working-on_14.html
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Repairing car Door lock Actuator?
http://howtobyme.blogspot.com/2011/11/repairing-car-door-lock-actuator.html

How to Access car door panel?
http://howtobyme.blogspot.com/2011/11/how-to-access-car-door-panel.html

Vehicle door panel components?
http://howtobyme.blogspot.com/2011/11/vehicle-door-panel-components.html
----------Front Door dis-assembly diagram?

http://repairhelpcenter.blogspot.in/2012/02/front-door-dis-assembly-diagram-for.html

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Rear Door dis-assembly diagram?

http://repairhelpcenter.blogspot.in/2012/02/rear-door-dis-assembly-diagram-for.html

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How to test Power door locks? http://repairhelpcenter.blogspot.in/2012/02/how-to-test-power-door-locks.html
--------This will help.Thanks.

It is not a short - you have a bad connection causing intermittent operation of the wiper and lock. Suspect that both devices are on same electrical circuit..

Get the facts straight and open up the indoor panel and start checking for voltage when button is pressed. Might need a schematic to further trace the wiring and source of 12 volts..

try replacing the lock/unlock relays. They will be located on the driver's side of the dash on the side when the door is open. These relays run the rear doors. Replace both while you are at it....I just had the same problem and replacing one would not do the trick. New part # is 1911-6058

push the button. wait like half a second, then push it again. most cars lock only the driver door for the first push, then all the others for the second.

lubricate door hardware, locks, etc.

maybe check the fuses or a loose wire.

The rear doors will not lock with the keyless remote, the drivers master switch

There is a plastic piece on the backside of the door handle that is probably broken or it came off of the bar that conects the handle to the pin in the door that allows the door to open