This is on my 2007. I'm not sure when this starting happening to be honest. I just noticed it today. Both of the other brake lights work, as do the reverse lights. It's only the stock third one mounted to the tire carrier. I've checked fuses and also tested the wires with a multimeter and there is obviously voltage since it's on but I wanted to see what the number was at. I also borrowed a friend's light and plugged it into mine. His flickered when connected to my Jeep's plug as well. His doesn't do this when connected to his Jeep however. I was thinking it was the brake pedal switch but wouldn't the other brake lights not work or be flickering if that was the case? I thought maybe it was the plugs themselves too so I shaved some of the insulation off the wire before the plug and cut the plug off the light itself. I touched the bare wires together and same thing. It went on but flickers lol. I have all stock electronics and stock sound system too. No CB radio or anything for interference either. I searched for something like this but couldn't find any topics that had anything specifically like my problem in them. Sorry if I missed a thread on this. Thanks in advance.

 

Perhaps it is going to ground somewhere inside the tail gate on the wiring harness side?

I cannot remember how it goes together, but if it plugs in inside the tailgate or the outside and not inside the tub, I would check for grounding. Also, check for pinched wires and damaged insulation from the plug to inside the tub.

 

Does the flickering have a steadiness to it, or is it more of a random thing?
Connect an analog volt meter to the plug at the light fixture and see what the needle does.

Just for the heck of it, replace fuse M1. See if that makes a difference.

The Center High Mounted Stop Light (CHMSL) is a basic hard-wired circuit, with a switch. It doesn't involve any computer.
The CHMSL switch contacts route 12 volts to the high mounterd light assembly in the rear. There is a splice in the circuit that sends the 12 volt signal to the TIPM to activate the regular brake lights. If your regular brake lights work OK, the switch is not the problem.
You may have to probe the wire from the light, forward every few feet, to see where the power becomes steady again.



Since this is a basic circuit, you should look for a bad connection in the power side, or a bad connection in the ground side.

 

Thanks ronjenx and ZMagic97. I will work with it more tomorrow morning. I have looked at the wire all the way to where it goes under the stock carpeting directly behind the passenger side tail light and didn't find any parts that were missing insulation, etc. There is however, tons of sand and dirt inside the wire loom. Also, where the wire runs through the tailgate and along the back of the tailgate with that black plastic cover, there are many areas that look like someone took a flat head screwdriver and pressed on the wire, but stopped before cutting it.

ZMagic, the flickering is constant and thanks for the picture and explanation. The more I know what it isn't, the closer I am to fixing it : ) The M1 fuse wasn't blown when I looked at it but I will replace it anyway like you said and see what happens. I have checked the wire from the plug in the tailgate all the way to where it goes under the carpet behind the passenger side tail light with a digital multimeter but I forget what the reading was. I have it written down in the garage. It was somewhere around 7.32 when the brakes where applied. I do remember that the reading was the same everywhere I checked the wire.

One more thing to note, if I take the brake light and touch it directly to my battery it lights up fine with no flickering. Thanks again to both of you. I'll be back tomorrow

 

Okay, working with it again today I tried changing the fuse which didn't do anything unfortunately. The multimeter reading on the wire inside the tailgate at the plug and at various places along the wire leading up to the small nylon wire cover near the tailgate hinges fluctuates from 7.32 - 9.21 over and over which I'm guessing is mimicking the flashing of the light. I can't really think of anything else to do besides following the wire all the way underneath the carpet behind the passenger tail light and running along the entire right side of the interior. This is all obviously covered in loom and tape and I really don't feel like taking up the carpet, cutting all the tape, breaking all those little zip tie fasteners, and then opening up the loom to try and find where there could possibly be a short or ground problem. It doesn't seem like a bad enough flicker to take it the dealer, not to mention the problem is probably really simple.

 

If tracing the wire forward is not something you want to do, go right to the switch, then. See if it's pulsating there.

Look at the picture I posted above to get an idea which wire it is in relation to the plunger.

 

I'm going to go do that right now

 

When touching the wires gently on the brake pedal switch that supply power to the high center mount brake light and the other two brake lights, the flickering worsens and then turns to flashing. If I continue to move those 2 wires, none of the brake lights work. The plunger on the switch itself is really dirty and gummed up too. Power fluctuates here as well. Are these difficult to remove and install if I were to go that route?