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Old 04-17-2002, 08:41 PM   #1
Scooby Newbie
Member#: 9186
Join Date: Aug 2001
Location: Ottawa canada
00 Legacy GT

Unhappy Need help with rear O2 sensor wirting diagram for 2000 Legacy GT


I'm trying to troubleshoot a CE light due to an Brullen exhaust
installation. The code is P0420, and I need to find out what the
rear O2 sensor wiring corresponds to.

I spoke to a mechanic regarding the wiring diagrams for
the rear O2 sensor. I had a look at them myself.

The wiring codes indicate colours of the HARNESS (i.e. the wires from
the ECU) not the rear O2. It seems the colours of the sensor wiring
change, but the harness colours are consistent.

Trouble is the while the diagrams give the colour code, they do not
readily indicate the PURPOSE of each wire. Was wondering if anyone
way could help. The purpose is so I can get the right connections so
can install Brullen's fix. (This is a circuit that is placed between
rear O2 ands ECU, it is supposed to clear the CE light. We tried it
on my car but the CE light came back. My guess is that it was
incorrectly, and this is why the light went back on. It has since

Here is what I got for the harness wiring:

- White (Pretty sure this is ground)
- Black / White (Goes to the Shield and Sensor ground joint connector
under the dash: Pretty sure it is ground)
- Yellow / red (tied to the front A/F sensor, we believe this is the
12V wire for the heater.
- White / Blue (goes direct to ECU)

Can anyone confirm?

Thanks all.

Dean Hummel
Ottawa Canada
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Old 04-17-2002, 11:36 PM   #2
Scooby Specialist
Member#: 2003
Join Date: Aug 2000
Location: Calgary, Alberta, Canada
'99 BGP Legacy GT
'98 QS Legacy L (auto)


jazzman - the wiring loom should fit right in. If you have the CEL fix in, more likely than not, you're front O2 sensor has a problem. IIRC there was a recall by Subaru done on front O2 sensors.
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