I recently replaced my motor and trans mounts and now, about 2 weeks later, a P0137 code popped up. I find it odd that it just so happens to be the O2 sensor that I had to disconnect when replacing the driverside trans mount. Is there anything special I should have done when reconnecting the O2 sensor? like using some dielectric grease on it?

Any other suggestions or should I plan on changing the O2 sensor? I have no idea how old they are.