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2010 prostar, and The truck marker lights must have caught covid virus. The turn signals work, headlights work and tail lights work. The visor lights and side marker do not work. All wiring and bulbs are factory, no aftermarket installed.
Any suggestions on where to start trouble shooting?
Thanks
I also Could not find a fuse.
Good luck finding it! You have a short to ground somewhere. No fuse, it resets when you turn the key 'off'. When you turn the key back on, quickly look for any lights that are dimmer than the rest (or not on), this may help you locate it.
The harness pins on my driver side marker light, the one under the door, the pins were corroded, both lights were dim. I pulled old pins and replaced with new along with purchasing new lights at the dealer, no issues since, new lights nice and bright. May be corroded pins in harness... I would start there.
Thanks, I'm in the process of checking every bulb. The two side cab were burnt out, I replaced them. Now instead not coming on at all, they come on flash twice quickly then go off.
Fix. For now, but I need to find out why 4 lights went out. The two side cab and 2 on the visor.
Your right, probably covid, that sneaky little...
I missed the part on your first post that said your tail lights were still on. Probably not a short to ground, probably bad connection or broken wire making intermittent connection. A nightmare to diagnose!

On my truck I had an unsecured wire on the tail light rub through to ground. It took me a long time to figure out no fuse, have to cycle key to reset circuit. Doesn't sound like this in your case.
I found an old post where Rawze said to start checking every bulb. my headlights work, tail lights works, also the turn signals work. I found the 2 cab side marker lights were both out. the filament for the marker light was broke, and the turn signal was not broken. continuing checking the lights 2 visor light were out, 2 staring from the left side of the truck. Everything works now. looking for any shorts or broken wire to explain what cause this. I don't think 4 lights would stop working at the same time.
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