I've been working and searching for an answer, am at the end of what I can think to do.

Symptoms - when I put the left blinker on, the radio and odometer blink, the right brake light blinks, the license plate light blinks, the left front parking light doesn't blink, the front and rear blinkers are working. If the headlights are on, the symptoms are a little different. The right blinkers seem to function as normal. If I pull the fuse for the "left parking lights" some of the symptoms go away like the radio and odometer blinking, but the right brake light still blinks.

What I've tried so far - I replaced the $20 relay under the dash, no joy. I replaced the turn signal switch, no change. I'm changing bulbs at this point in the desperate attempt to stumble upon the fix.

I assume it is a short somewhere in the loom of the car and don't know how to chase that down. My mechanic said there might be a body control module, I suppose it could be that. He also said he'd inject a signal tone to chase down the issue.

Any ideas?

 

I've seen similar issues in this forum, that's how I knew to replace the relay and the blinker switch, just nothing that I've seen seems to be the fix. Otherwise, I wouldn't have posted this one.

 

I fixed it. It was the trailer wiring harness box thing. Just disconnected the little box and the lights returned to normal.

It was not the flasher relay.
It was not the turn signal switch/stalk
It was not the wiring harness.
Hopefully this will help someone else to chase this down.

 

Thank you for this tip. Where is the wiring harness box? Is it under the rear hatch door? I want to give it a try.

I have the same issue. I found a video and it shows the turn signal flasher is above the brake pedal in the fuse box. However, my fuse box doesn't have a place/insert for the round flasher (LL552 Part Number). I only see a Power Accessory outlet.