First thing I would verify is that no wires going to the o2 sensors have been cut, frayed, or damaged in any other way (causing the short). It's not uncommon for a wire to maybe rub against the exhaust, which would in turn melt it over time, causing it to short out. Haven't heard of that happening on the
KJ just yet, but I do hear it a lot on other Jeeps.
When I looked up P0158 I got "
O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)"
Bank 2 Sensor 2 is going to be the downstream sensor on the passenger side of the exhaust.
If you'll go to this thread right here, you'll see a description of the o2 sensors that I posted straight out of my factory service manual for another member who was having problems before with an oxygen sensor. You'll also see the picture in there that shows you where the two downstream sensors are.
Hope that helped!