Sliding door is grinding as it opens/closes. Can we lube something we can't see or should we replace some part?

Check to make sure there is no rocks and or dirt in the track path, spray WD40 or other lube on the rollers and moving parts.
Most of the time these will be the fix, however, the switch could be bad. You may wish to shop around for a more affordable repair shop! There mite be two electrical contacts on the door and pillar, will look like two metal buttons, clean all these contacts.
Good luck!

Normally, this is caused due to Sand or not enough lubrication. If you do not have some technical knowledge on it , it will be wise to take it to a repairman

Test the door by manually opening and closing it and seeing how it feels. If it's hanging up at some point it could be something in the track or just may need the rollers Lube

There is no "switch". The Sliding Doors should be manual anytime you try to open or close them. If not: then there is problem in the electronic system or the physical/mechanical side where something is jamming the door from opening or closing.

you may have a worn bearing you may have to remove the track arm assembly to repair

lube everything that moves on that door with white lithium grease, also lube the door latch.

i just fixed one. it had a broken wire in the harness that moves with the slider, you have to completly pull the harness apart to find it

Something similar to that was happening with our Odyssey...the beeping when you are driving whether it's ongoing or intermittent is the "safety alarm" letting you know the door is not closed. The power lock is not engaging. What I do when I get the beeping while driving is hit the Door Close button. It causes the door to attempt to engage again. To fix it...we first cleaned out the space below the side running board (kids were hiding crayons and things in there), then looked for any obstructions along the top and bottom tracks. I sprayed a lubricant along the tracks (I'd suggest the dry lube kind...I used WD40 the 1st time and had streaks of it dripping down after driving), use a lube that has a long straw to spray in small places...and spray up into the track that runs the length of the middle of the car. Manually open and shut it a few times to get the tracks lubed, then try it out.
If you press the open OR close button by remote or in the car and get nothing...no movement/no noises/no beeping...then it could be the electrical circuit itself, the signal itself may be impeded...or the motor shot. Have you tried any of these suggestions before?

I found out that the auto sliding doors are just like garage doors.... need lubed, connectors in door jamb cleaned and sprayed with silicone lube and sometimes an ajustment for tension- dealer item.... I took mine to a dealer and drove out 30 min later.... hope this helps.

Take a rag with rubbing alcohol and start wiping out all the creavas. Get it spick and span, those dern things are super sensitive a little peice of popcorn kernal will not let it close