IIRC the SL version of the 105 series uses the "axle/bearings/cartridge" unit and does not have a dust cap to remove and be able to access the bearings and do an adjustment. But this unit is actually easier to service then the more traditional dust capped type. At the inside of the pedal body where the axle extends out there should be a notched ring (likely of black plastic). This is the exposed part of the bearing/axle unit that a special (good luck with channel locks instead) tool slips over, engaging the notches, that when rotated in the properly direction will pull out of the body the axle/bearing unit complete. IIRC the RH pedal will have LH threads for this plastic ring and the LH pedal will have RH threading, it often is marked on the ring which way to remove. Once pulled out the end of axle lock nut is very accessible to do the adjustment. Before reassembling dump (I use a small grease gun) some grease into the pedal body's cavity (where the axle/bearing unit was). As the now well adjusted axle/bearing unit is rethreaded into the body the grease that you just placed inside will get squeezed out through the bearings. If you placed enough grease in first there will be a lot oozing out from between the axle and that plastic ring.

This takes about 5 minutes per pedal if you have the right tools and work slow. I do this often on repairs at work. I hold the pedal body lightly in a bench vice. The most difficult aspect is remembering which way to unscrew the plastic ring on what pedal. Andy.