Problem resolved!. The clue was that "both" O2 sensor should come off of c133 not L bank from c110. Upon investigation I discovered a connector hanging from the back left side of the engine against the bell housing (conn c128). I also discovered two loose bolts on the bell housing. It appears that the auto trany was rebuilt. Upon reinstallation the tech did not connect the O2 #21 back to the appropriate connector, but instead connected it to the aux fuel tank connector under the chassis! (closest conn available to O2 #21)
The 2' jumper that extends the c128 conn to the O2 #21 conn is missing and I will have to get one from a salvage yard. But It makes complete sense now. One for the books.
Take care
Ed
