CEL code 0031

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GeneralGrievous
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CEL code 0031

Post by GeneralGrievous » Tue Dec 09, 2008 6:08 pm

Back from the dead and with my normal level question... :oops:

During driving the General threw the trusty CEL. Once I got home and had a minute I checked with the AP and it shows code 0031 front oxygen sensor low input code

Didnt try to clear the CEL thinking if its legit it'll just throw again and if the sensor is bad its probably running rich or sumthin...

Any suggestions? Get a new AF sensor ? :crazy:

Hope everyone is doing great BTW...

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snaab
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Re: CEL code 0031

Post by snaab » Tue Dec 09, 2008 10:38 pm

This is unlikely to be an "illegtimate" code.

Check the sensor for obvious wrong-doings such as large amounts of mud/rust/gunk. The AF sensor is likely the culprit either. because this code would result from improbable readings from, not merely a lean condition that would have been produced by the AF sensor.

Find out the specs for the O2 sensor resistance and check that with a good DMM (i.e. high impedance). Also make sure it's wires aren't obviously chewed at and grounding out somewhere.

Anything to contribute, Dr.WRX?
RJ
'13 Mazda3

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Libra Monkee
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Re: CEL code 0031

Post by Libra Monkee » Wed Dec 10, 2008 11:30 am

I'm not the good doctor but I might be a fairly competent orderly. "Low Input" sounds like something's blocking the O2 sensor. Either it's not getting enough air for a reading or it's not getting enough air, period. I could be as simple as just cleaning off the O2 sensor or as costly as replacing it altogether.

OH, and welcome back!
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Re: CEL code 0031

Post by ElZorro » Wed Dec 10, 2008 1:17 pm

I don't have anything else to add beyond those guys, other than welcome back!
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drwrx
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Re: CEL code 0031

Post by drwrx » Wed Dec 10, 2008 1:31 pm

If you want to do a bit of trouble shooting you could always clear the code (OBDII tool or just pull negative battery terminal & hit brake) and watch to see how long it takes to come back. If it doesn't come back or it takes days or weeks, it may be nothing serious. If it comes back in a couple of hours your going to have to do some work.

Have you noticed really crappy gas milage lately? Is your car not running well or is the idle really lumpy or low (below 600 RPMs or so). If so, the sensor could be fouled or on it's way out. How many miles?

Also, check your wiring harness to the o2 sensor (occasionally they can melt if they get too close to the headers).

If you don't want to buy another o2 sensor you could pull the current one out and see if it's black as the heart of Satan and try to clean it. Throttle body or carb cleaner will work (some even say "safe for o2 sensors").

A replacement o2 sensor with harness is like $80 IIRC.

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Re: CEL code 0031

Post by snaab » Wed Dec 10, 2008 4:39 pm

The exterior (that is to say, the part that is not in the exhaust stream) of the sensor has a small port to open air. It can become clogged. Usually on street vehicles, they don't, but it's far from impossible.
RJ
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Re: CEL code 0031

Post by Mr Kleen » Thu Dec 11, 2008 6:56 am

I have nothing to contribute about the CEL, I just stopped by to say hello to a long lost DCAWD'er. :mrgreen: :wiggle:

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GeneralGrievous
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Re: CEL code 0031

Post by GeneralGrievous » Thu Dec 11, 2008 10:52 am

I have noticed teh crappy gas mileage btw.. I'll reset and see what gives.

Y'all are always smarter than these Texas folk :wink: :mrgreen:

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Re: CEL code 0031

Post by zaxrex » Thu Dec 11, 2008 4:09 pm

I can't remember if that 2was my code or not, but when the anti-fouler plug started rusting, I had O2 sensor code problems. I took it out, tapped it on my knee, blew some of the carbon bits out and put it back in. That was over three years ago.

May you have similar luck.
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Re: CEL code 0031

Post by complacent » Tue Dec 16, 2008 2:53 pm

Whoa! it's teh General! *waves*
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GeneralGrievous
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Re: CEL code 0031

Post by GeneralGrievous » Tue Dec 16, 2008 5:37 pm

Update

So after a busy week I got up on the ramps and checked out the O2 sensor. Wires seem fine, sensor wasnt scuzzy, antifouler no prob either..

Unhooked negative and reset. CEL back after about 1minute of run time. :notcool:

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Re: CEL code 0031

Post by snaab » Tue Dec 16, 2008 7:52 pm

Did you check its resistance though? I can't tell you what it should be, but compare it against the other O2 sensor.
RJ
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Re: CEL code 0031

Post by drwrx » Wed Dec 17, 2008 11:05 am

GeneralGrievous wrote:anti-fouler no prob either..
Wait, your running an antifouler on the front o2 sensor?

That is a no-no. Get that off there right away. There is no reason to have an anti-fouler on the front o2 sensor. I'm all in favor of using them on the rear o2 sensor (it's basically useless), but the front actually has some real purpose in closed loop fueling. If you have an anti fouler on the front o2 sensor your ECU will always read you running lean and add fuel accordingly or throw a CEL.
GeneralGrievous wrote:CEL back after about 1minute of run time.
I also couldn't tell you what the resistance is supposed to be on the sensor, but the CEL coming back that soon would indicate yours is toast. Or perhaps something even more difficult to diagnose and fix like an electrical issue (signal is blocked or degrading from sensor to harness to ECU).

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Re: CEL code 0031

Post by Sabre » Wed Dec 17, 2008 11:40 am

Hey there! I have nothing to contribute (since the good doctor and snaab have taken care of you). I just wanted to say hello!!!!
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Re: CEL code 0031

Post by zaxrex » Wed Dec 17, 2008 1:58 pm

OK, found my shop manual.
DTC PO031 - FRONT OXYGEN (NF) SENSOR HEATER CIRCUIT LOW INPUT

Following Darrin's questions about the front 02 sensor, I thing you might be looking at the rear one. There is no way I could fit an anti-fouler plug between the exhaust manifold and the sensor and clear the frame. There is just not enough room.
If you didn't have to take the front right wheel off, then you were def looking at the rear one. Sorry if I mislead you with my previous post and my rear 02 sensor.

If you do take out the front O2 sensor, here are the diagnostic steps from the manual. excessive, but complete...
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Re: CEL code 0031

Post by snaab » Wed Dec 17, 2008 5:16 pm

I missed the whole thing about the antifouler but ZaXXX and the Doctor seem to have taken up my slack.
RJ
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GeneralGrievous
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Re: CEL code 0031

Post by GeneralGrievous » Thu Dec 18, 2008 5:58 pm

Check out the brain on Zak!

Yes very complete.. I'll give it a go this weekend. While I drive the wife's car lol

And "hello" Julian!

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