Would could possibly cause my car to be able to not pick up any codes when I plug in the obd machine? It says error check connection. My car will get no spark at all! I changed the entire distributor... Cap,rotor,coil,control module, checked all fuses, I changed the fuel filter although I'm getting fuel. My g101 wire was loose originally and I tighten back up. It's like the ground wire for the ecu. My crankshaft wire was a bit chewed up so I'm changing that. Someone please help this is driving me insane trying to fix it

If you're not getting any reading other than error on connection, then that is where you need to start. All that other stuff you're doing is just guesswork and costing money. The error could be caused by a bad ECM and no matter what other parts you change, you'll get nothing out of it.

Try a different scanner and if you get the same error, you will need to check the connections, the fuses, and the ECM itself before spending money in hopes that you might get it.

I tried three scanners and they all did the same, I checked all of my fuses and they are all completely fine. I'm not exactly sure what connections it means to check. But I have literally did a complete check on everything I can possibly think about. I even changed the main relay. I'll turn my key over, main relay clicks, fuel pump is good, engine light will come on 2 seconds then go out. All this happened cause the ecu ground was loose... For about three days till I found what it was. Could it have messed the ecu up?

Yes, it very well could have fried it.

Hypothetically, OK I have another ecu but it's not thee exact one for my car by far but it was the same plug in as mine. If I plug that one in anyway should I be able to pick up spark if it is the ecu

Try turning the ignition switch to Position II, after you attach the scanner. I suspect the ECM is fine, since the CEL comes on for 2 seconds and then goes out. If there was a problem with the ECM, the CEL would stay on. My bet is the problem is with the Crankshaft Position Sensor.

Check all powers and grounds to ECM before replacing it.

Ima change it today, but if a wire I bad would that cause it not to be able to read codes

Maybe no codes were thrown.