need help with P0031 code on 01 Mazda MPV

I have a 2001 Mazda MPV w/ check engine light on. The Code is P0031 - bank 1 sensor 1 heat control circut low voltage. I can't seem to find anything about it online other than some one tried replacing the O2 sensor (which i thought might be the problem) and they still got the same code.

Can any one help me w/ exactly what i need to do to fix this problem?
would be much apreciated thank you.

so you have replaced no parts then?

correct. I have not replaced a part since the 0031 code. The spark plugs were recently replaced.

The oil was changed and then got the 0031 code.

you need to check the voltage to the 02 sensor

Can anyone tell me where I can view a photograph/image/diagram of where to look for the O2 sensor in order to check the voltage to it?

The P0031 code is on my 2000 Mazda MPV ES minivan. It has the 6 cylinder, 152 cu in displacement engine, with a 4 speed automatic OD transmission.

Also have 2001 MPV w/P0031 code. Wondering what the typical cause of said low voltage turns out to be. Hope to find loose oily or corroded connector/s but a heads up if some other grimlin is known to play a role.

FWD:

The O2 sensor heater in the Right side exhaust manifold is the one that would set a P0031 code. The right side manifold is the one towards the rear of vehicle and not the one up front by the radiator. How many wires are coming out of the O2 sensor in the left side manifold by the radiator? Should be 4. There should also be 4 in the other sensor as well. I think perhaps someone has spliced in a very cheap universal O2 sensor that does not even have a heater and that is why you are getting the code that you are. If you will follow the wires from the sensor to the engine wire harness you will probably find that they are spliced into two wires that are Light green with red stripe and Brown with yellow stripe. Look around in that area for two other wires probably not connected to anything. One of them should be Yellow and the other Black with White stripe. These are the two wires that should be connected to the heater circuit of a 4 wire sensor.
The Sensor further down the exhaust pipe but before the converter is called the middle O2 sensor and would set an entirely different code.