I have a 2000 Maxima GLE. It is a Caliifornia car with 4 02 sensors. I cannot find the location of 1 sensor. There is 1 just behind the radiatior (Bank 1). 1 into the front of the catalitic converter, and 1 just above it about 4 inches away. Where is the 4th one. Someone said between the engine and firewall (Bank 2).