Turn Signal Headache

I played with all bulbs the other day and eventually switched back to regular 3157 bulbs. With regular bulbs, all worked fine, back to LED's the gremlins came back. I ordered new LED's so will see if that improves life.

Playing with it today, I tried brand new 3157 LED's and no changes so started process of elimination. Switched to regular lights for brake lights and all resolved. Not sure where to go next, but all are LED minus brake lights.

Relevent necro is my hero. First post in this thread is from 04 Awesome!

Bad ground somewhere, probably concerning one of the bulbs. Check the sockets, clean if necessary. Check the condition of the grounding tails. Clean connections and reinstall.

I have a similar issue with my 99. The left rear directional does not work at all. The left front directional only works with the headlights off and it does not work with the headlights on. The arrow on the dash just stays solid. It has a factory 7 pin tow harness. I unplugged that and connected everything back together and it changed nothing. All connectors are clean and have no corrosion. I swapped the multifunction switch with a known hood one and the problem still persists. All brake lights including the third brake light also blinks in sync with the directionals.

After 17 years, the rules of thumb for diagnostics are still the same:

Always start with the basics, testing the bulbs or fresh bulbs, cleaning/inspecting/testing bulbs sockets, wire plugs, and wire harnesses for damage or corrosion. Locate all the grounds, clean them and snug them down. Inspect the wire plugs and optional relays located behind the spare tire and plastic trim, leaky windows and rusty fenders allow water to contact non-sealed wire plugs. Always suspect any trailer light wiring. If any symptoms seem to be related to a short circuit in the power windows, radio or tailgate, check the driver door and tailgate wire harness for faulty or damaged wires.