I have a 2001 Silverado and I can not get the driver side rear turn signal to work. All other bulbs, turn signals and lights work. Only the driver side rear is not working. It flashes very fast on the interior of the truck which is what alerted me to the problem. This is what i have done so far. 1) I have changed the bulb. 2) I have disconnected the wire harness from the junction box under the rear of the truck. No visible damage. 3) I removed and inspected the flasher module. It looked okay but I honestly don't know if you can tell if its broken by just looking at it. 4) A couple weeks ago I hooked it up to a trailer to see if the trailer turn signal worked and it worked fine. Also, as soon as I hooked it up to the trailer the turn signal (blinker) started working on the truck. It worked fine for a week or so and then stopped again. Don't know if it was just a coincidence that it started working after hooking it up to the trailer. Any suggestions on what to try next? Thanks!