I too am a shade-tree mechanic. It's worth noting that early electronic fuel injection didn't require any external software or device. Rather, you would use a m

I too am a shade-tree mechanic. It's worth noting that early electronic fuel injection didn't require any external software or device. Rather, you would use a model-specific technique to put the vehicles computer into diagnostic mode, and it would blink codes at you from the check engine light, or perhaps show the code on an LCD that was normally for another purpose. This was late 80s and early 90s stuff using OBD1, the earlier diagnostic standard. On my Toyotas, I would need to jumper a couple pins in a connector under the hood with a paper clip, labeled T1 and E1, I recall. On my BMW, I had to turn the key to ON and then stomp the gas pedal 5 times in a few seconds. After counting the blinks, the meaning of the codes could be found in manuals. IMHO this was a great system and every bit as useful as what you get with basic OBD2 scanners, just without the scanner investment. I needed no tools to be told my catalytic converter or primary o2 sensor failed, etc.