I got a 2000 Honda Civic ex coupe with a b20b swapped in. I got a s300v2 running a base map tune.
I just went to the junk yard and pulled the engine harness out of a 99-00 hatchback automatic. Mostly everything plugged back into the motor couple plugs unconnected are not in use
She cranks over but doesn't start up
I know I have the wrong Distributor but I have the correct distributor and I am putting it on now but it still won't start up

 

Was it running before or didi you just swap the engine out? Disconnect the MAP sensor and see if you have the 5v on one of the wires with the switch "on". Use an LED testlight or noid light to see if you have injector pulse at the injectors. Do you have spark? How about trying any b series ecu for said year see if it starts. How about your timing marks are they still good? Are all the grounds connected to the chasis and the one on the thermostat housing. If I had spark I would spray carb cleaner into the intake(brake booster port or throttle body) but do this on your own risk-have a fire extinguisher handy