M20 O2 sensor wiring question

[cdeason7]

The O2 connector has 4 wires (black, gray and 2 white), I want to confirm that black is power, gray is signal and white is ground. Thanks

[vpilarrt]

Black is signal, gray is ground, 2 whites (interchangeable) are heater.

[cdeason7]

Thanks, so what supplies the power ?

[jeffnhiscars]

Id say the sensor itself, being just a variable resistor, doesnt need power. The ECU reads it and adjusts accordingly

[cdeason7]

Something has to power the heater part of the O2 sensor

[e30davie]

Probably best off to grab a wiring diagram from various sources and have a look.

It's probably powered from one of the main relays as its a fairly large current draw.

[cdeason7]

I agree, I did find the attached photo but no reference to wire color

[jeffnhiscars]

Something has to power the heater part of the O2 sensor

Vpillart pointed out there are 2 heater wires so I thought you were asking what powered the sensor side.

[flumph]

There should be an O2 sensor heater relay. In that little relay box next to the AFM. There's 3 relays: one is the main relay, one is the fuel pump relay, and one is the O2 sensor heater relay. Why they needed a separate relay for this, I'm not sure.

Also, narrowbands don't actually behave as variable resistors. They're voltage sources, like tiny batteries.

Poke around the wiring diagram for your car to be sure though.

[cdeason7]

Actually, I am just reusing the connector, I am installing a Wb02 sensor for the microsquirt pnp ecu.