Toyota Repair: O2 sensor location and heater, 2000 mazda mpv, late model cars

Question
Ted, You were so much help with my Tundra could I impose on you for some help with my Mazda? I have a trouble code P 0031 on my 2000 Mazda MPV. The readout is "the voltage signal for oxygen sensor 1 heater control in bank 1 is to low for the current engine operating conditions." Is this sensor the one on the exhaust closest to the radiator or to the firewall? Also is this heater  necessary only for the first few moments of the engines opration and therefore an element of operation I can ignore with minimal consequences?


Answer
The O2 sensor number one is always in front of the catalityc converter.
The sensor needs heat to work, in order to speed up the heating process all late model cars were required to have a heater circuit so that the sensor would start working before the exhaust heat made it work, this is purely for emission control requirements to reduce emissions on cold starts. After the engine is warmed up the sensor should go into normal closed loop operation, the remedy is to replace the sensor but is has no effect on driveability in this condition, if you live in a state that has emission control checks for registration it would be advisable to replace the sensor because it will not pass the smog test.