This is for my 2004 GMC 1500, but I figured it was the same as the Dmax trucks for body electrical equipment.

This afternoon my right directional stuck on while my foot was on the brake. I thought it was merely a burnt bulb. However the indicator kept lighting (solid) every time I stepped on the brakes. Once home, I put the directional on for left and then right. The left works fine, the right works but causes the brake lights (including the third brake light!) to flash in sequence. stepping on the brake causes the brake lights to work and lights the right side directional in the back only.

So, I tried to isolate a short that I assumed to be in the right side tail light by unplugging the back harness (next to the spare tire). I unplugged each plug that disconnects the tail lights, and bumper lights, however the right directional would still cause the third brake light to flash.

I then pull the fuses for the trailer hitch directionals, which can sometimes corrode at the hitch and cause problems. This changed nothing. I pulled the actual directional fuses next, and replaced them. All fuses were fine. nothing changed. Flicking the high beams on and off seemed to help, as all of a sudden the directional worked fine with out triggering the brake lights and vice versa.

I took the truck for a ride and the directional thing came back, but is inconsistent.

A unrelated electrical issue is that I have removed the heater blower resistor to replace it, but I'm awaiting the new part tomorrow.

Anyone have an idea what I should do next? I'm at a loss on this.