2002 kia sportage

I have a 2002 KIA Sportage that dies sometimes when placed in gear or during deceleration .
Also the shift interlock is inoperative. I have checked all the wiring, connectors and relays. Someone has removed the radio by cutting the wires at the plug . During my exam I noticed that grounding the black and white wire in the radio part of the
harness kills the engine. I have isolated the wire to prevent it from grounding out.  It does Have 3 pending codes in the ECM
P0300 P0304 P0303 all three are misfire codes. The vehicle does start and run and will shift when the interlock is overridden manually