Depending on the year of manufacture, the attachment points may differ.
Front bumper
-open the hood.
-under the hood take out the caps (inserted from top to bottom).
-at the bottom of the bumper, Unscrew the screws and take out the caps (twisted and inserted from the bottom up).
-turn the wheels to the side.
-in the wheel wells, Unscrew the screws and release the fender liner (front).
-unscrew one screw on each side (spun up) that attach the corners of the bumper to the wings.
-we release the latch in the wings (pull the corners of the bumper towards you).
-with an assistant, pull the bumper forward (look for the wires).
-disconnect electrical connectors.
Rear bumper
-open the trunk lid.
-in the trunk, remove the rear panel trim.
-for the casing, Unscrew the four nuts.
-unscrew the two screws in the opening of the trunk.
-at the bottom of the bumper take out the caps (inserted from the bottom up).
-wheel arches take out the caps and release the fender liner (rear).
-unscrew one screw on each side that attach the corners of the bumper to the wings.
-we release the latch in the wings (pull the corners of the bumper towards you).
-with an assistant, pull the bumper back (look for the wires).
-disconnect electrical connectors (if any).
How to remove front and rear bumper Toyota Avensis MK1 (1997 - 2003)
How to remove front and rear bumper Toyota Avensis MK2 (2003-2008)
How to remove front and rear bumper Toyota Avensis MK3 (2008 onwards)