Engine swap

[Spotcat]

I have a 2018 Silverado 4.3 that had a bad motor

i bought a low mileage 2016 engine

i put it in and it had multiple codes and reduced engine power due to I used the 2016 engine harness

After changing the harness it idled smooth but then started running rough it shows only a code now of p16E4?

any ideas?

thanks

[CamGTP]

This is what I see come up for that code.

 

Low or no fuel, Faulty Fuel Rail Pressure (FRP) Sensor, Fuel Rail Pressure harness is open or shorted, Fuel Rail Pressure circuit poor electrical connection, Faulty Fuel Pump

Start testing the circuit or swap the fuel rail pressure sensor from your 2018 engine.

[rlcole321]

Did the used motor you got have the water pump in the same place?(on the side of the motor and not in the middle), the LV3 which is what came out of the 2018, was produced for multible years. But if the water pump is in the center then it is not a LV3 so you have a completely different fuel system.