cheap OB2 scanners??

The cheap ones that are based on the ELM327 chip work for getting codes. They are Chinese knock off. There is Bluetooth one from Vgate for about $20, it has an on-off switch, so can be left connected at connector without battery discharge. I use one with my phone and tablet, with Torque app.

Over a decade ago I bought an ELM321 chip and built my own, the parts for it about 3x what they cost today complete. The ELM327 chip is multi-protol for most post 1996 cars, since they vary both in hardware and software interface. The documentation is quite good, so one can easily build the hardware or write special software.