P0031 CEL! Now what?!?

10760 Views 21 Replies 5 Participants Last post by TRebelo, Mar 31, 2017

TRebelo

Discussion Starter · Mar 21, 2017

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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McBill

· #2 · Mar 21, 2017

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?

TRebelo

Discussion Starter · #3 · Mar 21, 2017

McBill said:
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

TRebelo

Discussion Starter · #4 · Mar 21, 2017

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

XJman

· #5 · Mar 21, 2017

I found this, is it helpful?

http://www.clubwrx.net/forums/maintenance-service-repair/82038-cel-p0031-p0032-fix.html

Sent from my SAMSUNG-SM-G935A using Tapatalk

TRebelo

Discussion Starter · #6 · Mar 21, 2017

XJman said:
I found this, is it helpful?

http://www.clubwrx.net/forums/maintenance-service-repair/82038-cel-p0031-p0032-fix.html

Sent from my SAMSUNG-SM-G935A using Tapatalk

I went thru that post already it didnt help me out because mines still popping up and it seems everyone replaces there's and it's good thank you tho I appreciate it

nsibanez

· #7 · Mar 22, 2017

I think the MAF would be something else to consider as well

TRebelo

Discussion Starter · #8 · Mar 22, 2017

nsibanez said:
I think the MAF would be something else to consider as well

Really...? Hmm it would effect the front o2 like that and throw a code?

nsibanez

· #9 · Mar 22, 2017

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

rqjoe

· #10 · Mar 22, 2017

??

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TRebelo

Discussion Starter · #11 · Mar 22, 2017

rqjoe said:
??

I'll go thru all this today

McBill

· #12 · Mar 23, 2017

nsibanez said:
I think the MAF would be something else to consider as well

It wouldn't be the MAF.

TRebelo

Discussion Starter · #13 · Mar 23, 2017

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

TRebelo

Discussion Starter · #14 · Mar 23, 2017

This one

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McBill

· #15 · Mar 23, 2017

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.

rqjoe

· #16 · Mar 23, 2017

for reference this is for my 15.

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TRebelo

Discussion Starter · #17 · Mar 23, 2017

3

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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TRebelo

Discussion Starter · #18 · Mar 23, 2017

If someone can find me a wiring diagram that'd be great!

McBill

· #19 · Mar 23, 2017

1) Go to this link WRX & STI Factory Service Manuals
2) Download shop manual for 2004 WRX/STI
3) Unzip
4) Open up folder labeled "wiring"
5) Open up PDF labeled "WI Wiring Sys"
6) Refer to page WI-80 and WI-87

McBill

· #20 · Mar 23, 2017

rqjoe said:
for reference this is for my 15.

FYI, this is not applicable. 2015 wrx is a completely different motor and the wiring to the front o2 is nothing similar to prior year's.

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