I've been getting this code:

"88 - GM Wiper, rear, relay activation, or short circuit to Ub"

I've cleared it twice.

The rear wiper seems to work fine. Not sure what to look for?

 

You're looking for this

https://www.ebay.co.uk/itm/Orranje-R...t/162287181715

 

Although a wiper delete will solve your issue, I live in an area that rains all winter and the rear wiper is essential to rear view.
One thing that has showed it's ugly head with rear wipers, is the wiring harness that enters the hatch, can cause the wires to chaff and wear the insulation. it will happen where the harness goes into the hatch and if you move the rubber insulator out of the way, you can often see the break, or short. A pretty easy fix.

 

I live in an area where it rains all summer and snows all winter... but yeah, I know the delete is a personal preference.

The wiring harness pass through could well be the issue here.