It bothered me that my ECU showed that problem starting closed loop early and bench testing showed no problems.
Well I did a couple scope shots. One with the scope ground on the signal ground pin and one on the power ground pin. The stock wiring has two signal ground pins (one connected to the shielded sensor input wire). The power ground is where the FV driver conducts current. Well I connected my buffer op-amp to the signal ground and my micro to the power ground. That is a problem as you can see in the attached scope shots. My micro has the A/D ground reference to the power ground.