Ok, so I replaced the pre-cat sensor on bank 1 (passenger side) and drove around fifty miles yesterday without the engine light coming back on. I'll update after some more miles. The sensor wiring looked intact under the sheath so I guess it might have been a short or interruption inside the sensor itself.

As for replacing the sensor, what a pain! Definitely a two person job. I had to attach my crowsfoot sensor socket with two universal attachments and several extensions all duct taped together. I then pulled the sensor cable ( it's around three ft long) up near the passenger side firewall so I could feed the crowfoot down from above. I found it helpful to tape the slit on the crowfoot tool closed so it wouldn't fall out on the way down. Then I slid it down the cable as someone below the car helped it into place and held it while the other person loosened the sensor with a breaker bar. Once it was loose, I was able to spin it of with two fingers from below and the new one went in fairly easily. Now I know why the dealers charge big bucks for that job! Whose idea was it to put those pre-cat sensors there?

Edit: Been a couple of days and a 100+ miles and no engine light!!!!

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