My durango won't start or crank . Replaced the harness now won't start can anybody help?

Did you disconnect the battery when working on the vehicle? If so, some of the systems may have to relearn or be reprogrammed? Loss of battery voltage may effect your security system? Battery has a full charge and connections all good? All engine and chassis grounds are good. Did you check voltage at fuses? Use a test light, some fuses hot all the time, some go hot with on, check both ways. see the starter relay in diagram, you can unplug it, use jumper wire between cavities 30 and 87, the starter motor should crank the engine, that doesn't mean it will start. If you try that, make sure transmission is in park or neutral and parking brake is set. Vehicle can't move. I could keep talking, but, I think that's enough for now? good luck