I'm having the same problem with mine, had the intake manifold off 3 times in the past month. Started off just the back sensor throwing the code, replaced both sensors, then got both codes, went back in checked the sensors, one wasn't clipped in right so I replaced the harness, codes still came back.

I'm thinking maybe bad batch of knock sensors or bad PCM. Could always be something going out in the motor itself.

 

i think its the after market sensors im gonna just go get oem ones.

 

With knock sensors as hard as they are to get to I would just go with OEM. I have also heard that IF they are dropped that they could be thrown out of spec and throw codes from the start. Sorry for your luck on this. When mine went out I just replaced the rear one. It fixed the problem. 6 months later I started getting codes again. I replaced BOTH of them and the harness after reading on this fourm. Havent had any issues since.