My honda accord's rear door lock make a grinding sound when i lock it. it doesn't do it when unlock it

yes

The power door lock electric actuator motor is defective most likely. You will need to pull the door panel off and test it with a volt meter for power and ground when the power locks are actuated, if the system is powering up the lock motor but it doesn't move the rod then replace it,.

THERE IS A CLIP ON THE INSIDE OF THE DOOR ON METAL ROD THAT GOES TO THE LOCK MAKE SURE ITS NOT DAMAGE OR FALLEN OF WHERE THE ROD GOES TO THE LOCK THERE ARE 2 ROD ONE OPENS THE DOOR THE OTHER ONE LOCKS THE DOOR

system seized or motor has gone

For Doors not getting open with remote or key problem,there are help links provided below.Click the link below to go through its procedure and troubleshoot the problem:----
drivers side front door will not open from inside or outside?

http://technoanswers.blogspot.com/2012/01/ford-f-350-crew-cab-drivers-side-front.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 ?
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
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How to Access car door panel?
http://howtobyme.blogspot.com/2011/11/how-to-access-car-door-panel.html

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Vehicle door panel components?

http://howtobyme.blogspot.com/2011/11/vehicle-door-panel-components.html

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Truck Door will not close?

http://schematicsdiagram.blogspot.com/2011/12/ford-truck-door-will-not-close.html

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Where is Cars Door control Module located?

http://schematicsdiagram.blogspot.com/2011/12/where-is-cars-door-control-module.html

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Power door locks not working?

http://schematicsdiagram.blogspot.com/2011/12/power-door-locks-not-working.html

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Door ajar light stays on?

http://technoanswers.blogspot.com/2012/01/door-ajar-light-stays-on.html

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Door locks not working?

http://technoanswers.blogspot.com/2012/01/door-locks-not-working-on-ford-explorer.html

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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

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Doors will not open with Remote?

http://schematicsdiagram.blogspot.in/2012/02/lexus-doors-will-not-open-with-remote.html

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How to replace Door Hatch ?
http://repairhelpcenter.blogspot.com/2011/11/how-to-replace-hatch-on-acura-integra.html

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How to remove Doors?

http://repairhelpcenter.blogspot.com/2011/11/how-to-remove-doors-on-acura-integra.html

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How to Replace Doors?
http://repairhelpcenter.blogspot.com/2011/11/how-to-replace-doors-on-audi-a4-and-vw.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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This will help.

Thanks.

The door lock actuator in the door that is making the sound is starting to fail. Replace the lock actuator for that door will help.

Sounds like a sticking switch ( actuator ) in the door.
Pull off the door panel and , looking inside the door, follow the rod from the key to the actuator .
Clean the actuator and make sure it works freely before re assembly.

Please reprogramme the remote locks.

replace the pass side door lock actuator

it sounds like the door lock actuator at the latch is worn out.