Thanks for the info.
The codes indicated that the Bank 1 Sensor 1 was malfunctioning [P1133 & P1135] and I was told by the dealership that this is the unit at the firewall. True?
[For some reason, I cannot trust a dealership service manager - maybe it's because the my new '84 Volvo GL caught fire and burned to the ground in a dealership parking lot with its first oil change. BTW: I did get a brand new car, baby seat, a complete set of Craftsman tools which I had just bought that morning, and an apology. I never went back there - but that was the same Volvo my Son crashed].
My wife's ES was made in Oct 98, so that puts in the midst of the sensor problems of that time. Evidently, the complaints got bad enough that Lexus issued a TSB (#EG004-99). The bulletin only states if routine checks do not solve the ECU code to replace the original AFI [#89467- 41020] with the supplied replacement [# 89467- 41021]. It would seem that there IS an issue with the Bank 1 sensor on this particular model, if a TSB was issued for the cars made from 8/1998 to 7/1999 ( Cal - 8/1997).
FWIW I believe there is something amiss with the ECU & AFI interface.
At this point it doesn't matter, my wife loves her car and I have to keep it going for her, so I will snatch that bad sensor out every three years if need be.
There are a few online parts suppliers that offer a Denso replacement unit [C5015-137284] for around $200, but I have never dealt with any of them.
Can anyone tell me if they have dealt with Auto Parts Place (.com), The Parts Bin (.com), Buy Auto Parts (.com) or Parts Discount Warehouse (.com)?