I have a 2007 gls with a 2.7. I am trying to find an engine diagram for it. It is showing a 131, 137, 300, and 301 engine code. I have pretty well figured that the o2 sensors are shot, but I still wanted to go through the motions and rule out anything else first. I have been trying to look online and find out where the number one cylinder is. I am guessing that it is in the front on the far left, but I am not certain of that or the firing order. Also, if I am not mistaken, that would mean that bank one sensor one and sensor two should be between the radiator and motor, and also after the cat on that same pipe. Is this correct, or am I way off base?????? Thank you in advance for any help that you might offer.

 

This pic should help:



Bank 1 is the bank of cylinders on the firewall side
Bank 2 is the bank of cylinders on the radiator side

Sensor 1 is the O2 sensor before the cat
Sensor 2 is the O2 sensor after the cat