[sraney]

My 2001 Tundra finally generated its first error code a couple of weeks ago at 116,000 miles--P0155 O2 sensor. Using this forum as a guide, I dutifully replaced the Bank 2 Sensor 1 unit. The truck then promptly (within 12 miles) generated a code (P0135) for the same sensor, opposite side (Bank 1 Sensor 1). My search of the O2 threads over the years shows that this is a pretty common occurrence--a code for one side followed closely by the corresponding code for the opposite side.

I'm not really much of a mechanic, and I wonder why this pattern occurs (as I prepare to order yet another $100 OEM sensor). While I would expect a similar MTBF for each side, I can't believe that the sensors fail independently so close together. Can the computer only display one code at a time? Was the other code just "waiting" to appear once I fixed the first one? Can the computer only diagnose one sensor failure at a time?

I welcome any comments from you experts out there to satisfy my curiosity.

Thanks.