I tested my 2001 Maxima's O2 sensors tonight. The precat sensor cycled between .1 and .9 volts.
2 of the others tested OK. They were at .28V then dropped when I pulled a vacuum hose and the voltage went up when I sprayed carb cleaner in the hose.The suspected bad one stayed at .16 regardless of the above mentioned tests. Does that appear to be a "smoking gun"?
I have a PO420 error.