Puttster

I've been going nuts trying to figure out the air-fuel sensor descriptions for my 99 Rx300. Here is what I have come up with, searching and searching.
There are three sensors. Two are "upstream" of the cat: Bank1, sensor 1, which is between the engine and the firewall, and Bank 2 sensor 1, which is on the front of the engine. The third sensor, which is, I believe, of the older O2 type, is downstream of the cat and is incongruously referred to as "Bank one, sensor 2." Sensor 2 does not go out very often and it is a different part number than the sensor 1's.

The codes p1130 and p1135 show defective heater circuits (the two black wires) in B1, S1. p1150 and p1155 show defective heater circuits in B2, S1 respectively.
The codes p1133 and p1153 shows defective sensing circuits in B1, S1 and B2, S1, respectively

The S1 original part is Toyota 89467-48011 recommended replacement part is Denso 234-9009.

Please comment if I do not have it right or complete.

carguy07

Looks correct to me.

tim73

Heres a diagram...