Seat belt won't lock - 2002 Chevrolet Cavalier Coupe

Question edited for clarity, full make model details.
Question moved from Spanish car maker Seat, (pronounced 'See-At') to make model category.

switch on passenger seat base - MBWorld.org Forums

https://mbworld.org > ... > SL-Class (R129)
Feb 2, 2006 - It's for when you put a baby/car seat in. It keeps the seat belt tensioner in one place after the seat belt is activated.
Seat belt locking in position
Feb 28, 2017
SL rear seats - family car, occasionally!?
Feb 24, 2017
More results from mbworld.org

Child Smart Seat for SL ' Mercedes-Benz Forum

https://www.benzworld.org > ... > R129 SL-Class
Jul 10, 2012 - Then there is a button to lock the seat belt of the passenger seat to secure the safety seat on it and deactivate the air bag. That lock button ...
passenger seat belt ' Mercedes-Benz Forum - BenzWorld.org
Feb 11, 2008
Seat belt is too tight ' Mercedes-Benz Forum
Mar 17, 2009
Seat belt stuck ' Mercedes-Benz Forum
Mar 27, 2007
Odd seatbelt issue ' Mercedes-Benz Forum - BenzWorld.org
Apr 24, 2013
More results from www.benzworld.org

and lastly

https://www.benzworld.org/threads/child-smart-seat-for-sl.1662040/

..

if it was mistakenly not installed at the factory you can get one installed or more likely it is under the seat somewhere.

Junk yard. Google "junk yard" and your location and you should get some hits. Or I like car-part.com. Once you get them, you should be able to access the bolt that holds them in place by moving the seat all the way forward (assuming that we are talking about front seats). There should be a plastic cover that "pops" off with a little influence. Remove bolt, install new/used part.

On my 2016 Ford Escape the rear passenger seat folded down and would not hold back up the problem was that the seat belt buckle pivoted down below the level of the seat when I try to raise the back of the sheet the seat belt buckle would prevent it it ended up crushing the plastic on the seat belt buckle preventing it from working the hold the seat belt I was able to repair the seat belt buckle with a screwdriver regular Style and a cigarette lighter the soft in the plastic back up so it would stay in position

REPLACE SEAT BELT ASSY

2005 Towncar SRS Code 33 (3 flash + 3 flash, repeat this set for twice. then Beep 5 times pause x 5 = 25 beeps every 30min).

This means you have problem with left (Driver) side pretentioner (Seat belt retract system).
It doesn't mean physical belt or retract mechanism.It is just bomb wiring which is part of airbag system.
When airbag deploy, passenger must stay tight in seat otherwise body lean to front then slam back to seat by airbag.
if belt is loose or delay to lock, passenger's body rocks back and forth.So, system use small bomb (Fire power) to lock and retract seat belt when airbag deploy.There is small bomb and igniter in part of Seat belt retractor.
Code 33 is warning for this part on 2005 Towncar.(older model is different meaning in Ford/Lincoln, it's possibly passenger side airbag system for earlier model)
Before you work for any part of Airbag system and touch any "Yellow connector", * *Disconnect battery (negative side is good enough) and wait at least 5 min to clear all power in system**.(Airbag store back up power for few minutes to be able to deploy even in case if power disconnected)
by the way, you should move your driver seat most forwarded position before you disconnect battery to make it easy to work with seat belt.
locate driver side seat belt retractor (in center pillar between front and rear door, you may have to fight with weather strip)

Locate Yellow connector on bottom of Seat belt retractor (it's called "Pretensioner")it is located on very bottom of rear side of retractor.
only one yellow connector. (make sure your battery is disconnected)
Check its physical connection or looseness.if connection looks fine, you may have to replace whole seat belt ($180-$200 in Lincoln dealer)
You can check if pretensionor is good or bad by regular tester, but unless you know how, I won't tell (because I don't wan't you to blow out pretentionor).

Take it back to the dealer .

Are you trying to say the seat belt retractor is stuck? This is in the front seat?
If it's anything like my Tahoe, you need to remove the plastic panel that covers the retractor (carefully - don't break the clips or you won't be able to put it back on). Take a large flat head screwdriver and slide it under the part where the seat belt coils up, and find a little tab - push it with the screwdriver. As long as the seat belt is not twisted up, it should retract.

This should be replaced. It is an eletronic part and will malfunction after accidents.

you may have to remove the bolt that holds the buckle to the floor. Try to push the belt into the retractor and see if it frees up.

I assume you are saying it is in the locked mode. It has an automatic lock mode for holding a child seat. When the belt is pulled all the way out, it goes into locking mode. You will hear it ratchet when the belt starts going back in.



Section 01-20A: Restraints, Active 1999 Taurus, Sable Workshop Manual
DESCRIPTION AND OPERATION Safety Belt, Lap/Shoulder The dual locking mode retractor on the shoulder belt portion of the combination lap/shoulder safety belt for the front seat passenger and rear seat outboard passengers operates in two ways:

1. In the vehicle sensitive (emergency locking) mode, the shoulder belt retractor will allow the occupant freedom of movement, locking tight only on hard braking, hard cornering or impacts of approximately 8 km/h (5 mph) or more. The front and rear outboard seat belt retractors can also be made to lock by pulling/jerking on the belt.
   

1. In the automatic locking mode, the shoulder belt retractor will be automatically locked and remain locked when the combination lap/shoulder safety belt is buckled and does not allow the occupant freedom of movement. This mode provides tight lap/shoulder belt fit on the occupant and on a child safety seat or infant carrier installation restraint.
   

1. When the combination lap/shoulder belt is unbuckled and allowed to retract completely, the retractor will switch to the vehicle sensitive (emergency) locking mode.
   

WARNING: REAR-FACING INFANT SEATS SHOULD NEVER BE PLACED IN THE FRONT SEATS.
The automatic locking mode must be used when installing a child safety seat on the front passenger seat and rear outboard seats where dual locking retractors are provided