Pairing BT to android head unit.

Hi, I have a bluetooth problem.
I need to pair to an Android car head unit that does not have the ability to select and pair.
My Arduino set-up works with an Android tablet as the tablet can find my HC-05 and allows me to select and pair.
The head unit has this function crippled, I can find the head unit and pair to it with a phone or a tablet.
I need the Arduino to be the client/master, to be able to select the head unit and enter the pin.
FYI I am using the arduino to relay pressure, AFR and temperature and I have a simple apk that I've created to be a dashboard.
Everything is bench tested and works except for connecting to the head unit. Ironically I would liked to have used usb uart but all comms threads seemed to use BT.
Thanks for reading - and for any advice. If it comes to it the head unit will be returned and I will source one that allows full Bluetooth functionality but I'd like engineer a solution if possible.

Assuming the device is plain-vanilla BT2 and thus compatible with HC-05, I think you have two exercises:

  1. Find the full address of the device. You may be able to do this with the phone, which I understand can connect.

  2. Configure HC-05 as a master and then to auto-connect with the device of known address. Check the Martyn Currey website.

Cool, it looks like I should be able to achieve pairing by using the pair, bind and link AT commands, I will give it a go tomorrow.
Happy new year.
I will post my results

Good luck. I keep forgetting that there is an AT command to inquire the address. I have never actually used this.

All sorted, ironically I stumbled on a method for pairing via the head unit embedded in an app. That said the AT protocol worked well for pairing with another BT HC-05 which I used before trying to connect with the real system and allowed me to rename the HC-05
Thanks again for the advice.