Signal Light Problems After Audio Upgrade

Greetings. I recently had the audio upgraded in my 2015 GTI mk7 S, and they did a great job on installing everything. However, later that day I had a warning on my driver dash saying 'check rear right turn light'. I am looking for a possible cause, but I think that it is either a cable which came loose while driving, or possibly the auto headlight system not liking the new electronics since the issue happened right at dusk.

I kept the factory head unit, and added a JL Audio FiX-86. Has anyone run into anything like this, or might have some insight to the issue? The shop is going to look at it for me, but I am hoping to have something more substantial than 'the lights arent working'.

Thanks!

The entire light assembly uses one harness. If that harness was loose then you should get a warning for everything and not only the turn signal.

The turn signal use it's own wires in the harness of course and depending on how/where they installed the JL fix it's also possible that they cut those wires. However, the car should check all lights as soon as you start it even when they're not being used (at least that's what I observed in the Mk6 when my rear fog lights went out and I never use them - still displayed that warning as soon as I turned the car on).