[DRW1000]

Your need for OBD1 vs OBD11 depends on what system your car(s) uses. All cars sold in North America from 1996 onward (95 in California) are OBD11 prior to that most are their own protocol of OBD1.

Most OBD1 have a way of reading the codes using the CEL, a voltmeter... You just need to find out how. A google search for the vehicle in question would probably give you a million hits.

There is a lot of DIY OBD11 scanners/software. I find them without even looking by typing OBD11 into google. I found one that actually gives the circuits and the software or will seel you the parts or the kits. They even have the schematics and board layouts. I will post if I cas find it. You can also by an off the shelf reader from many sources.