Repeated O2 Sensor Malfunction 3 Within Last 6 Months

[gurubaba]

Hi,

I have a 99 ES300 and here is the history of my o2 sensor replacements

May 2004 - O2 sensor bank1 sensor 1 (rear sensor)

October 2005 - O2 sensor bank1 sensor1 (rear sensor)

January 2006 - 02 sensor bank2 (near radiator)

April 2006 - car at dealership, said o2 sensor bad and wil replace it under warranty.

The service consultant tells me that the mechanic has done a thorugh check and could not determine why I am getting this repeated O2 sensor failure.

I have read some of the online threads here some of them allude to possibly a cracked exhaust manifold. I would have expected the mechanics at the Lexus dealership to figure something out, since they had every opportunity to identify problems for getting more revenue.

Any suggestions would be greatly appreciated.

Thanks

Guru