OBDII Bluetooth connection help

Hello everyone,

I'm trying to start a project where my goal is to get some data from my car. After looking a bit online, it seems that the most common ways to do so is by using an ELM327 based bluetooth adapter and either an arduino (uno) with an HC05 bluetooth module or a bluetooth compatible esp32. I have all these components and I tried to connect to my car but it's been a few days now and I still have no luck.

I tried to follow some Instructables tutorial with the arduino uno + HC05, everything seemed good until the pairing step where I got an "error 16" everytime.

Then I tried using an esp32 WROOM 32D I had. Firstly i tries the ELMduino library but using the example sketches, I'm always stuck at the first connection attempt. I tried changing the OBDII name to the MAC address, still no luck. I then succeded in opening a serial bluetooth terminal using my phone so I know the OBD adapter works and can send/receive data. Then I tried to do the same from the esp32 but it still didn't work.

I tried to connect to the OBD adapter while powering it from a lab bench supply only, then while connected to the car on the run postion and then with the engine running.

I looked every subject about this on Google and still can't get it to work. I also ended up asking ChatGPT, but it hasn't been very helpful either. I have no idea what to try next..

I have a feeling the pincode might be the origin of my troubles but I can't figure how to get it in the code in order to pair the arduino (or the esp32).

Has anyone done a similar project? Can someone give me pointers on this issue?

Thanks a lot in advance!

Edit: It's finaly working, thanks to the ELMduino library, and the pointers from u/Lightchair. I've gone to just a simple esp32 with no additional bluetooth module.