Replaced at 200k miles
I just changed my water pump. There had been a rattle for some time. Looks like something got in between the inverted pulley and the WP housing, because it was beat up inside and I found the pulley to be out-of-round and scored, as well as the snout. Must have locked up...
I'm in a similar situation with my 03 4Runner .. got the dreaded P0420 code. I do think it's my cat. But since sensor 1 is not really an O2 sensor, some A/F sensor, I can't tell exactly what's going on from the charting I've done. Bank 1 will have a sudden 0 reading, and on the next data set...
