OK, so for our proposes the definition of insanity is doing the same thing over and over only to come to the same result. Well, This seems to be an issue a lot of people are having.
I'm working on a 5.9L Grand Cherokee, Obviously we all know the year!
Ok, went through this same issue, "rear lamp failure" nonsense. checked around the entire jeep, 5 times, and stupidly started replacing rear upper brake lights, of which there are 3. Often times you go to another person when you think your going crazy, like I did. Both Auto zone guys couldn't figure the problem either. After feeling like I wasted money on the rear upper brake lights(which I did) I brought it home, and a nothing is like a systematic check of the vehicle's lighting system. Tedious and boring.
Since the problem also could have been caused by the dangling trailer wires, I started there. I used bulb cleaner and a plastic brush to clean off the points on that connection in back, then wiped them, and tested. No dice.
I moved on to the tail light as I already had replaced the top rear brake I knew they were good. I Pulled the right rear lights off, checked them applied that bulb cleaner to them tested all the bulbs. They were good, frustratedly moved on to the left side. As I pulled off the bulbs and listen carefully those who add after market Euro Lights to your Jeep.
As the design reflects alot of light off, and in the dark it doesn't fully illuminate well. I was unable to see, in previous checks that the bulb had burned out. Yes I felt stupid.....
How to remedy this. Well, it's a bish to put all of it back togeather head over to napa, autozone or kragen to get a new one. So Heres how a bright guy dealt with this. Also this is really crucial to getting your man card back so listen up. Go to your, glove compartment
No offense ladies..
(I can't believe we call them that who puts gloves there, reg, manuals, insurance... seriously)
There is a bulb that illuminates that compartment, bulb size (194), same as the marker light. Swap burned out bulb, for working 194 from glove compartment.
Now check... ah ha it works, no " rear lamp failure ", now, when you have time drive to the auto store when it's convenient, and get one for your glove compartment. (bulb size 194) There are other places on this vehicle you can get this bulb, but this is the easiest.