Default [Q] Car aux-in not detected as headphones

Something weird is going on here.
I have just bought an aux-in cable (ai-net to 3.5mm jack) to plug my phone (Wiko Darkmoon, MTK 6582 based) to my car stereo (JVC G511), but the phone doesn't recognize when I plug in the jack.
However, if I turn up the volume on the car, I can hear music both from the phone speaker and from the car's.
What does this mean?

I tried also with my brother's Moto G, and it correctly plays music through the headphone jack, but with a quite low volume.

Can it be something software related? My phone has 4.2, my brother's has kitkat. Or maybe something is wrong with the cable's pinout? I opened one end of the cable and I see three wires, and this should be enough from what I got to understand.

Btw, my phone works okay with normal headphones