Left turn signal blinks fast but, only when brake is applied - Problem also involves reverse light

[Tech-Mechanic]

I've had my KJ about five weeks, and one of the issues when I got it is that the left turn signal blinks fast when you step on the brake. The turn signal seems to work fine when the brake is not applied.

I realize the short could be anywhere in the circuit but, I thought I'd ask if there are any common places to look before I start troubleshooting tomorrow.

Symptoms are as follows: (all bulbs appear to work)
Left blinker flashes fast with brake on - works fine otherwise
Left front turn signal comes on solid when the car is in reverse. The left turn indicator in the cluster comes on too but, slightly dimmer than normal. (I don't know what the rear one is doing under this condition, I assume it's on also)
Reverse lights both work but, the left one goes off when the brake is applied

Since one of the places that all these circuits converge is the tail light assembly, I'm hoping the problem will be localized there since it's easy to access! Any ideas?

 

[Billwill]

If you do not have the logics for your Jeep...download the complete Service Manual here...2004 is not covered though!

What year/model is your Jeep?

The Wiring diagrams are in section 8W.

I suspect that the Left Turn Signal wire has a partial short with some other wire/s.
This can happen when when wires get squeezed together somewhere and the insulation on the wires fail.

2006 LHD CRD has a known issue with the harness behind the Fuel Filter Mounting Bracket!

Using the wiring diagrams you need to isolate the wire in question properly at all points..ie. this wire should be floating in mid-air with no signs of any continuity to ground.

These wire often go into large harnesses and can get damaged somewhere.

After my GF pranged my Jeep into a tree I had to replace about 15 wires completely as somewhere in the harnesses they were shorting out!

www.colorado4wheel.com/manuals/Jeep/KJ/

 

[sota]

service manual, find the ground nearest the left tail light housing.
that's where I'd start.
also pull the light housing and make sure nothing is wrong/damaged/melted/buggered.