Rear o2 Sensor harness

[DarkPhoenix]

Before I did my cat, I knew I had to replace the rear 02 sensor, so I got a Bosch universal for the it. I replaced the front with the OEM Bosch from the stealership.

I just want to confirm what I think to be the truth, since the FSM really doesn't say. What are the colour of the wires on the factory rear O2 harness? I have a red/yellow, and a white.black, which I am to assume are the heater circuits, and a shielded blue/white (grey shielding) which is the signal.

Am I correct in this assumption or am I off-base?

[Huffer]

Are you reading the FSM or going by the actual wires on your car?

[DarkPhoenix]

Are you reading the FSM or going by the actual wires on your car?


Both if I am reading the wiring diagram correctly.

YR/B/WL is in the FSM.

[Huffer]

If you are looking at the actual wires on your car, just match those with the Bosch unit. My last Bosch O2 came with a universal diagram, it should tell you which wires are which.

[DarkPhoenix]

I have the two white wires and one black. I was just curious which wire on the harness is the signal.

[Huffer]

I have a red/yellow, and a white.black, which I am to assume are the heater circuits, and a shielded blue/white (grey shielding) which is the signal.


I have the two white wires and one black. I was just curious which wire on the harness is the signal.

Now I'm confused.

[DarkPhoenix]

I have a red/yellow, and a white.black, which I am to assume are the heater circuits, and a shielded blue/white (grey shielding) which is the signal.


I have the two white wires and one black. I was just curious which wire on the harness is the signal.

Now I'm confused.


Universal O2 has two white, one black. The whites are for the heater and the black is the signal. On the harness end it is Red/yellow, white/black, and a shielded Blue/white wire. I just need to find out which one is the signal wire.

[Huffer]

Ok, gotcha. It should be the same as the front, which is:
Bosch 3 wire sensor (2 white and one black) uses the black for the signal wire.
Subaru also uses black for the signal wire.
The yellow/red and (blue)white both go to the white wires for the heater.
Doesn't matter which white, polarity doesn't matter.

[DarkPhoenix]

Ok, gotcha. It should be the same as the front, which is:
Bosch 3 wire sensor (2 white and one black) uses the black for the signal wire.
Subaru also uses black for the signal wire.
The yellow/red and (blue)white both go to the white wires for the heater.
Doesn't matter which white, polarity doesn't matter.

Thanks a lot Huffer. That is what I thought, but just wanted to clarify. Sorry for the confusion.