dalehicks

I was given a 1995 e320 that had a bad engine wire harness that had fallen apart, after i replaced the harness car had a code 17. since then i replaced the crank position sensor due to the tach not jumpimg during cranking. so far i have replaced engine harness, crank sensor,Ecm with a known good one of the same part number ans series. now after all that the tach does not jump now during cranking.did it go out again? car has a code 17 coming back after cranking. anyone know what this code is for? i was told that is related to #4 injector/ECM,is any truth to that. this car has me up in arms trying to figure it out. any and all help would be great. thanks to all who reply in advance.