I have a 98 Cherokee and when I turn my left turn signal on both rear lights flash. I think it's a ground issue but not 100% sure, any ideas on what it could be or where to start looking

 

Start at the lights and trace the wiring from there to the switch to the battery. The short is somewhere between those points.

 

It could also be the flasher relay pooping out.

 

Clean or replace your turn signal switch, multifunction switch as chrysler calls it. I had the same issue and the inside of my multifunction switch was gummed from old dielectric grease causing it to flash the rears like my hazards were on.

 

Thanks I will see what's up this weekend

 

i had this happen to me a while back it took a new relay to fix the problem

 

does this year have the multifunction flasher