JAB

Having put over 300,000 miles on a collection of RX300 I have on more than one occasion had to change an O2 sensor. I recall discovering that somewhere in the available documentation an error appears as to the locations of the sensors generating 171 and 174 codes, whether the one near the radiator or the firewall. I am in the situation again, and need to confirm the following: 171 is the upstream sensor near the radiator; 174 is the upstream sensor near the firewall. Correct? And, for either one the preferred sensor is the Denso 234-9009. Correct?

salimshah

When you interpret the error code, usually they say Bank1 or Bank2. In RX the engine is sitting sideways. Bank 1 refers to the firewall side of the engine and Bank2 -> radiator (front of the vehicle). Also the engine is tilted a bit and some things on Bank one may be easier to access from below. [easier is a relative term here].

Hopefully my post will help you zero in.

Salim

JAB

Further research does suggest that I was wrong. In the transverse V-6 used in the RX, cylinders 1, 3, and 5 comprise Bank 1, which is adjacent to the firewall; cylinders 2, 4, and 6 comprise Bank 2, which is adjacent to the radiator. Code 171 refers to the sensor on Bank 1, i.e., firewall; Code 174 refers to the sensor on Bank 2, i.e, radiator.

Anybody disagree?