'99 4.0 O2 Issue
 

Hopefully someone here can help on this one. I started with a bad MAF Sensor, tested, it fail so I replaced it. Now I'm hitting a P0136 code (O2S Ckt Malfunction 1/2. Tested harness, tested fine. Pulled sensor, looked fine (relatively new: about 1 yr old).

Any other ideas on what might be causing this out there?