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Discussion Starter · #1 ·
Soo it's a 2004 WRX, with a Perrin Intake and Cat-Back exhaust everything else is stock from manifold to uppipe and downpipe

I got a P0031 I replaced the front o2 sensor and I get the same code within 5-10 seconds of starting the car up. I checked the brown relay underneath the passenger side dash and it seemed fine even unplugged it cleaned the connections and re plugged it in nice and snug and also did the same thing to the actual o2 sensor plug code doesn't seem to go away I don't know what to do next or were to turn I need to get an inspection and this CEL needs to go away! Any ideas will be great
 

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It's likely the wiring harness/plug going to the sensor. What you need to do is get your hands on a voltage meter and test the connector to see if the sensor is getting any voltage from the harness. It should see 12 volts with the ignition on.

Side question: Did you clear the code after replacing the sensor?
 

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Discussion Starter · #3 ·
It's likely the wiring harness/plug going to the sensor. What you need to do is get your hands on a voltage meter and test the connector to see if the sensor is getting any voltage from the harness. It should see 12 volts with the ignition on.

Side question: Did you clear the code after replacing the sensor?
Car on running battery is at 13-14v and at the front o2 plug unplugged from the o2 and testing harness side it read 9-10v
 

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Discussion Starter · #4 ·
And yes I cleared the code after the new sensor and I started it up and it came back within 5-10 seconds I'm also getting P0546 - Exhaust Gas Temp Sensor Ckt High but did 2.2k 1/2w resistor mod and it's been clear
 

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Discussion Starter · #6 ·

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Maybe....whne mine started going out, it was a process and was acting like I had a massive intake leak for a while before it stalled and couldn't get it started. My car was acting pretty funny for a while before I was able to figure it out
 

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Discussion Starter · #13 ·
Can anyone confirm this the right wiring diagram for the front o2 so I can wire up a seperate harness just to eliminate a broken wire or short somewhere
 

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If memory serves me correct, there should be two that are the same color (white) that both hold +/- for the heater, which is what the code is in regards to getting a poor signal on. Then there should be one colored or black wire that is the signal wire and one grey wire that is your ground. I think.
 

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Discussion Starter · #17 ·
So the actual o2 plug on sensor side has 2 black, 1 white, and 1 blue but on the car harness side there's 2 white, 1 black, 1 yellow w/ red stripe, labeled plug b18 on the image
(These are not my actual images just found them online for a reference it's identical)
I just need to know exactly we're the wires go
 

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