Left rear turn signal error

[Josef]

I have a really strange error happening. When my headlights are off (either with the auto headlight selector or by manually turning them off) I get a rear left turn indicator error and a fast flash as though a bulb is out. No lights are burned out and everything seems normal externally.  The weird part is that I don’t get the error when the headlights are on.  I am assuming this is related to the canopy that was just installed. I know that they went in through that left rear tail light. Any ideas why the indicator functions normally with no error when the headlights are on but not when they are turned off?

[Transient]

Sounds like electrical got messed up with the canopy install.  I'm assuming the canopy has a high mount brake light, and they may have spliced into the left brake wire harness and screwed something up.  Just guessing, but that's where my mindset is currently at. 

[newdude]

Could be.  I'd check the trailer plug for any corrosion in the terminals.  We had a truck with a very similar scenario but no cap on the truck.  Had a corroded turn signal terminal on the 7 way trailer plug.  If they tied the cap into the trailer plug that could have set it off too.  

 

The trailer lighting control module I think can get pissed off easily hence why the corroded trailer plug on the one we had made the driver's signal work all sorts of strange with the lights on and off.  Wouldn't even flash sometimes at all, just stay full lit and the indicator in the dash was on most of the time solid and not blinking.

Edited January 12, 2022 by newdude

[Josef]

I’ll pop the tail light assembly off when I get back from my trip and check it out.  I’ll also check out the trailer plug. The fact that it works fine when the headlights are on and not when they are off seems telling but I can figure out why.

[Transient]

I recommend listening to Newdude.  Many here will vouch for his credibility.  He's far more knowledgeable than I on these type of things.

[Josef]

So checking back in on this.  The issue was definitely caused by my canopy install.  They tapped into the positive wires up in the cab down behind the drivers side fuse panel.  Those connections all seemed fine.  I checked those and on my next drive everything was working correctly except every once in a while when braking my backup camera view would open up on the dash.  This led me to believe it was a ground issue.

 

They tapped into the ground behind the left rear brake light.  The ground was a wiretap that had a male spade connector sticking out.  The female end that was attached to the ground wire had collected some dirt.  I cleaned it out and tapped it up this time (the installer hadn't).  Everything is working correctly now.

 

One other item I noticed.  When I use the trailer connector checking system the third brake light on my canopy doesnt light up.  It does when I press the brake pedal however.  Not sure why this is but I dont really care all that much so I am not going to dig in on that one.

 

Thanks for the advice and when it doubt check the connectors.

[taladro1]

I have a 2020 Silverado 1500lt left turn signal bulb was bad I switched it to a good one and doesn't blink 'checked the connector it's good there's power going tords it and the blinking too any ideas