My wipers go by themselves

Most likely the wiper motor assembly itself.

That would be too easy. Try under panel in front of windshield.

Remove the air inlet grille panel retaining nuts.
Remove the air inlet grill panel push-pin retainers.
Disconnect the washer hose.
Remove the air inlet grille panel from the vehicle, by pulling upwards in order to disengage the retaining clips.
Place the air inlet grille panel on a clean, prepared surface.
Remove the rear hood seal from the air inlet grille panel studs.

Remove the bolts retaining the wiper transmission assembly to the vehicle.
Carefully push the wiper transmission assembly rearward to disengage the wiper motor from the slot in the plenum.
Disconnect the wiper motor electrical connector.
Remove the wiper transmission assembly from the cowl panel plenum.

Position the wiper transmission assembly to the cowl panel plenum.
Connect the electrical connector to the wiper motor.
Insert the wiper motor post into the slot in the plenum, push the transmission assembly forward to seat the post.
Install the bolts retaining the wiper transmission assembly to the vehicle and tighten them to 71 inch lbs. (8 Nm).
Install the air inlet grille panel for Envoy and TrailBlazer as follows:
Position the rear hood seal to the air inlet grille panel.
Install the rear hood seal to the air inlet grille panel studs.
Position the air inlet grille panel to the vehicle.
Push downward on the air inlet grille panel to seat the retaining clips.
Connect the washer hose.
Install the push-pin retainers.
Install the air inlet grille retaining nuts and tighten them to 35 inch lbs. (4 Nm).
Install the wiper arm onto the drive shaft.
Hold the wiper arm blade in position to the dots in the windshield blackout area.
Install the nut on the drive shaft. For TrailBlazer SS models, tighten the nut to 26 ft. Lbs. (35 Nm). For the other models, tighten the nut to 22 ft. Lbs. (30 Nm).
Install the cover on the nut.
Operate the wipers and inspect for proper operation.
Connect the negative battery cable.

OOPS! First things first.
Disconnect the negative battery cable.
Remove the windshield wiper arms as follows:
Remove the cover from the nut on the wiper arm.
Hold the wiper arm and remove the nut from the wiper arm.
NOTE
Use a battery terminal puller to remove the wiper arm if rocking the wiper arm fails to loosen it from the drive shaft.
Push inward at the wiper arm pivot in order to loosen it from the drive shaft.
Remove the wiper arm from the pivot shaft.
Clean the knurls of the drive shaft with a wire brush.

Have fun.

You're very welcome. Have a great holiday!