The motor components are showed laid-out on the picture below. The circled cover and insulator disc are pushed over the back of the motor itself, and are there to prevent anything shorting the two main supply pins in service. The pins are fed with 12v, either one polarity or another, depending on desired drive direction. The other 3pins are irrelevant for this exercise; they are there to sense the drive worm itself;
D5252T_seat_back_motor_components.jpg
To remove the motor, first unclip the spring from the seatback hole (both arrowed below) and allow the friction cord to hang loose from the recliner mechanism. This allows the mechanism to be turned easier for reassembly of the square drive-bar, as each side of the seat has an independent mechanism that needs fine adjustment to slide the bar in smoothly. Then remove the nut from the other end of the bar as circled (i.e. the tunnel side of the bar) then pull the square drive-bar out through the drivers door aperture and recover the nylon protective sleeve;
D5252T_seat_back_recliner_mech.jpg
Remove the motor to the bench, and strip off the bracket (two fixings circled yellow below) and remove the star-washer (circled orange below) to release the harness;
D5252T_seat_back_motor_dismantle1.jpg
Desolder the two main supply pins on the back of the motor. This is not strictly necessary, but it helps a lot with the reassembly of the motor end cover and brush-box. Then fold the two retaining tabs out (as arrowed) to release the motor end-cover. There is no internal spring pressure, so nothing will fly apart. The easier way of many to fold the tabs out is to use a small'ish pair of locking pliers with good square jaws. Lock them solidly over the square tab, and use the pliers to fold out the tab;
D5252T_seat_back_motor_dismantle2.jpg
The end-cover is keyed so that it will only assemble one way, but it can help to make a small Tipex or paint mark to help align the cover to the motor body. Just ease the cover back off the motor, and most likely the brush-box will come with it - no problem. This will then expose the commutator, which can be cleaned with a light abrasive (P1000 wet and dry paper) gently on the segments that are blackened. Switch-cleaner solvent or isopropenol alcohol is best for cleaning this up afterwards.
Check the brush-box for sticking brushes, but be careful not to displace the brushes out of the box. If they come out, you will need to feed the brush coil spring back in behind each one again, but they will tend to stay within the brush-box if they are not poked. Clean any excess solder from the brush-box contacts, then assemble the brush-box back over the commutator, using a fine screwdriver to ease the brushes outwards as they need to pass over the end of the segments.
Place the motor end cover over the brush-box, then test the motor with 12v in either direction to confirm it now works. If all is OK, resolder the harness back on again, otherwise give the commutator another clean to be sure. The tabs can be bent back over the motor end cover using the same technique with locking pliers.