Need some volunteers and/or a funding angel to create a corpus of howto docs that identify the RF receiver parts in automotive ECM units and their associated wiring harnesses, including which pins to cut to assure radio silence in both directions.
I'm reading this discussion with some amusement because I wrote off car ownership and being a 'motorhead' a decade or more ago when the cars wouldn't let you tune them up correctly b/c 'computer'.
ECM units are fairly well RF isolated, so those that talk to the world should normally have easily identified connections to external antennas.
Junk yards pull ECMs and sell them back to their manufacturers
Vehicles have intrinsic baseline performance / emissions / operation they are capable of. Computers with sensors are just there to tweak things and tell you when it's broken. You could just as easily watch what those systems are sensing and actuating under various conditions, duplicate the control in your own FPGA/PIC/etc, then rip out the factory system and put in your own. Getting a motor to run or pass EPA isn't that hard... spend some time learn2motorheading on youtube. cpu, rom, flash, io, control, antenna, logging are increasingly being embedded under a single chip epoxy cap. Fewer leads to cut when the only leads left are io to sensors, actuators and power. If antennas become embedded there's always Faraday. Cut the service io ports. Internal logging would still require destruction. Manufacturers don't need used ECM's, the ECM rebuild / repair / replacement aftermarket does.
codermange who love his '67 Chevy C20 long bed farm truck more each day :)
Word. If you livin in some place that has EPA checks, newfangled Hyundai's, and more pavement and sewers than pasture and streams... you aint country.