2008 Lincoln MKZ 3.5L V6 with engine code P0353

Question

I have a 2008 MKZ with a P 0353 code. I have replaced all 6 plugs. Replaced the rear right hand coil with a new one. Still had the P 353 code. Then I put the coil from the right rear into the rear center position. still have the P 0353 code. What's next

Answer 1

Coil #3 harness will have to be checked 

with the key on the harness should be getting higher than 10 volts. 

ignition coil relay might also need to be looked at 

coil #3 is on the passenger side towards the engine