Cadillac 1999 DeVille Owner's Manual page 21

3. Just before it reaches the end, give it a quick pull.
4. Let the belt go back all the way. You should hear a
slight clicking sound. If you don't, the adjustment
feature won't set, and you'll have to start again.
5. Now you can add a small amount of slack. Lean
forward slightly, then sit back. If you've added more
than 1 inch (25 mm) of slack, pull the shoulder belt
out as you did before and start again.
If you move around in the vehicle enough, or if you pull
out the shoulder belt, the belt will become tight again. If
this happens, you can reset it.
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