My sunroof cover opens fully with the one-touch feature but won't close when trying to close the sunroof. How do I fix this?

Question edited to add maker, and correct 'completely'.

This is a known issue. See the link and videos.

https://www.google.com/search?q=Buick+LaCrosse+sunroof+won%27t+fully+close

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Most times when that happens it could be a mechanical blockage. In the tool kit that came with the car there should be a hex tool to manually close the roof. There should be an access panel at the front with a pop off cover. If you remove that cover there should be a female hex that the tool fits into to manually close the roof. If you have the female hex on the sunroof but no tool, most times the correct size allen/hex wrench will do in a pinch. Try opening the sunroof fully with the tool and verify there is nothing in the rails or lead screws the will keep it from closing fully. Also check for a blown fuse to the sunroof.

check fuse and relay if good than possible motor ot track problem their should be a mechanical bypass that will let you close it if stuck open the following information is courtesy of monte carlo forum

To check the condition of your original sunroof guides:

1. Gl*** in closed position.
2. Locate & remove 3 torx bolts on each side of sunroof glass. Lift glass out of sunroof opening & set aside in a safe place.
3. Locate "J" shaped cover plate at front of sunroof track assembly. Remove 2 torx bolts from each cover plate.
4. Lift up bracket to remove.
5. Inspect the plastic guides on each side. The sunroof cables attach to guides on front outer corner. Inspect this area closely for damage.
6. Do not operate the sunroof with the J plates removed.

Troubleshooting:

If the sunroof guides are not broken & the glass is a uniform height along the rear edge your problem may be a stripped gear inside the motor. The motor has a manual override:

1. Get access to the motor by removing the map light/switch console or lowering the front of the headliner.
2. Insert a large standard screwdriver into the nylon bushing at the center of the motor hub. Push up & turn the screwdriver to manually move the sunroof glass. If the unit will fully open & close manually, you most likely only need a replacement motor.

If your sunroof is stuck in the open position follow these steps to get it closed:

1. Remove the glass.
2. Try to close the unit without the glass. Many times one side will still be operational and close correctly.
3. Try to slide the inoperable lift arm forward. If it moves, slide it forward until it stops.
4. You now need to slide the original plastic guide forward to lower the arm to the closed position. Using a standard screwdriver, push it forward. The lift arm should begin to lower.
5. If the lift arm will still not fully lower, remove the J plate as explained above, sometimes the sunroof cable will need to be lifted up to allow the guide to fully slide forward.
6. Reinstall glass.

hinge is broke

1. Move the sunshade rearward to the open position.
2. Separate the mechanism covers (2) from the tabs (1) on the glass panel.
   
   
   
3. Verify the sunroof glass panel is in the fully closed position.
4. Loosen the forward attaching screws (2) on each side enough to permit the front of the glass to adjust up or down.
5. Adjust the front surface of the sunroof glass panel 0.00 mm to 2 mm (0.00 in. to 0.08 in.) below the top surface of the roof.
6. Tighten the front glass panel attaching screws to 5.5 N•m (49 in. lbs.).
7. Loosen the rear screws (2) on each side enough to make the rear adjustment.
8. Adjust the rear surface of the sunroof glass panel 0.00 mm to 2 mm (0.00 in. to 0.08 in.) above the top surface of the roof.
9. Tighten the rear glass panel attaching screws to 5.5 N•m (49 in. lbs.).
10. Check for proper fit. If not OK, repeat glass panel adjustment.
    
    
    
11. Position the mechanism covers (2) over the glass tabs (1) between the locating features and seat fully.
12. Verify sunroof operation and alignment.
    

There is a reprogramming from chrysler for the sunroof for recalibrating the sunroof for flushness also. the dealer will charge for this .You might want to do this first and then the adjust if not satisfied with the results.

as a florida resident for over 30 yrs and a mechanic I'm Not a big fan of sunroofs I'm a convertible man. a sunroof can be a real problem and costly to repair. may I suggest pulling the fuse and not using the this feature as they are prone to leaking. this situation sounds dangerous and should be off line until a solution is found.

These limits are not adjustable.

you need to replace glass or is it leaking if leaking then you have to remove upper seat belt covers pop off remove bolt 14mm and the trims on upper pillars pry off carefully held in by clips remove covers on interior light at front where sunroof switches are there are screws by bulbs disconnect connector remove center light cover and screws disconnect connector with clean hands remove rbber trim around sunroof opening and plastic cover on each side of sunroof glass held on with plastic screw clips then remove four 10mm nuts lift sunroof glass out of car remove cover and screws from rearview mirror all plastic trims around headliner move pass seat forward most and flip back rest all way down roll pass window fully down then slide headliner out of car now you can remove electrical connectors and remove water flow hoses from sunroof unit remove 8 12mm nuts holding frame to roof remove through door you will see the track sunroof slides on remove nuts along problem is silicone between track and frame is deteriorated lift track clean replace silicone reattach frame to roof dont put trims or liner in till test connect switches and glass to frame make sure sunroof works and closes fully then go through car wash to see if leak is fixed

Temporary Fix: unsnap off the access door in the overhead ceiling liner behind the sunroof opening;
Use a 4mm hexagon Allen wrench to wind it closed.

I think I know the answer....your gear has slipped on the cable a few teeth. Set the roof to the desired closed position, flush with your roof. Then open the panel above the mirror by first prying off the switch plate and removing the two 10mm bolts holding the mirror. Remove the sunroof motor gear, or rather just lower it out so it is disengaged with the cables. Now connect the switch and hit the auto open button as if you wanted to open the roof with single flick of the switch. Now hit the auto close button (same button of course, but the single touch method). The motor will advance and stop to where it thinks the roof should be, closed, which it is. Reassemble the gear into the slot, test it if all good, replace the mirror and panel.
Good luck.
Manfred.