My 02 4.7 spit out a CEL for bank 2 sensor 2. After much troubleshooting, it was determined that there was an open where the harness connects back to the ECU. Repaired and fine now. During the problem, voltage for the sensor heating circuit was normal, 13.5 VDC. The sensor voltage was a little low, 0.1 VDC, probably due to the intermittent nature of the problem. Something to watch out for!