P0031 - Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

It may not be the O2 sensor (you can test the resistance).

Check out the following article (from googling subaru p0031):

Bob

Yeah, I saw that, but I think that might be a little premature to start suspecting that right away.

Any idea why the cruise control and traction control went out with it? What do they have to do with the O2 sensor?

Yousuf Khan

I'd be looking for a common ground or power point - most likely a bad ground if resetting the code doesn't solve the multiple failure issue.

The Cruise control goes away when you get a CEL. I think it's Subaru's way of punishing you for having a CEL. Too bad there is not way of punishing subaru fro creating cars that so easily have a CEL.

In my old 2000 OBW, I've had CEL's and I've never had cruise control go away because of it (the OBW didn't have traction control though). This is actually my first-ever CEL on my Tribeca, so I've never seen this behaviour before. Maybe Subaru added this feature between 2000 and 2008?

Yousuf Khan

Weeliott seems to think that this is default behaviour whenever you get any kind of a CEL.

Does anyone have any opinions on getting aftermarket O2 sensors? The Subaru parts range from C$244+, whereas an aftermarket part seems to go from U$79+ (C$105) to C$140. Also the cheapest one is available through Amazon.com, but it'll take maybe 3 weeks to be delivered to me, is that too much time to wait, and should I just source it locally?

Yousuf Khan

My wife's 2008 Impreza throws up a CEL whenever she doesn't get the gas cap tight enough. And the cruise control will not engage until we stop and re-tighten the gas cap.

It's a royal PITA when we're on a closed highway where stopping for anything other than emergencies is frowned upon.

A good reason to try to diagnose the existing sensor first. Nothing quite like installing a new, expensive part and nothing changes.

I'm wary of most aftermarket sensors. If the OEM part is too pricey, try an aftermarket OEM supplier like Denso for Japanese cars. If you have a 2008 Tribeca, the p/n is 234-9047 for the upstream sensor and it's C$166 on Amazon.

It has been my experience generally that you end up paying the same or more when you use aftermarket sensors as OEM because the aftermarket direct fits are just about as expensive as the OEMs (if you get good ones) and if you buy universals you will end up replacing it again - and end up going to OEM or direct fit eventually to solve the problem anyway.

The OEM is not made by Subaru in the first place - so if you can get the direct fit "aftermarket" part made by the same supplier as OEM you are all set (I believe Subaru used NGK sensors as OEM) - but generally the price difference is not huge.

Teach her to put the gas cap on properly.. Also, putting the gas cap on properly will not turn off the CEL immediately - it has to go through the evap monitor test section of the drive cycle - so putting the gas cap back on will generally NOT give you cruise control back right away.

She'd had the car in for inspection because you

*really* have to lean on the cap as you turn it. Even then, you have to turn in until it has clicked at least a dozen times. And sometimes even that isn't enough. Personally, I suspect the cap itself, or the top of the fuel pipe, is "off". On my own car (not a Subie), I can almost finger tighten the gas cap to one click and I'm good to go. But the dealership insists nothing is wrong.

Also, putting the gas cap

Don't I know it. We stop for gas, have to stop again to reset the gas cap. Then stop again at the next rest stop to shut the engine down and restart it. And, usually, again at the rest stop after that.

As I say, I royal PITA.

Regardless what the dealer says, you have a problem.Check for any sign of rust on the top of the filler neck. If it looks perfect, try a new cap. There should not be that much effort required to seal the fuel system.

If you're a fan of the CEL, you couldn't do better than getting a VW or Audi - they have so many air and vacuum hoses that get brittle and crack and leak that you can bet you're gonna be driving around with one. CELs forever! ;)

Damned german rubber ---among a dozen or more things I hate about "wiener wagons"

My mechanic is afraid to work on my Passat 1.8T 4Motion wagon. I've been buying Chinese made plastic hoses and fittings to replace in my spare time. It's a work in progress. The engine mounts will probably go any day now so I'll be on the lookout for that. I'll also have to replace the diverter valve and maybe the secondary air pump and hoses. I'm hopeful that the turbo will hold up. Other than that, the engine's fine!

Yesterday, I saw a guy in the supermarket with the car hood up so I asked him if he was having trouble. He said he just bought the Audi A4 for his daughter to drive to school and he was checking fluid levels. The car is pretty much the same as mine so I told him to check the power steering level and I'd top it off for him since I just bought a can of special German power steering fluid imported from the Fatherland which cost $23 dollars per liter. Thank god it was OK since that stuff is expensive!

Anyway he had automobile mayo in the coolant tank so that's very bad news. I didn't say anything because he seemed rather proud of the car and who am I to spoil the moment? :)

The chinese rubber and plastic is often pretty awfull stuff too, but not as bad as the german stuff - generally speeking.

I can't imagine that the Chinese parts are going to be much worse than the OEM parts made by Bosch or Hella or whatever. They look pretty good to me, actually. :)

Yeah, called a bunch of dealerships and they confirmed that by default they turn off cruise and traction controls on vehicles that get a CEL come on.

Yousuf Khan

Yeah, I found a Bosch replacement part on Amazon.com (not Amazon.ca) for about C$105. The only problem is that they can't deliver it for at least

3 weeks. Should I take a chance with not having this part for 3 weeks or more, or should I go with a locally sourced part? Canadian Tire is selling one for C$140, don't know the brand though, but they can have it by the end of the week.

I'm thinking that I'm not in any danger of destroying the catalytic converter because this car has 4 sets of O2 sensors altogether, because there are two banks of cylinders. The other bank's O2 sensors are both working. I'm thinking that if whatever emissions are happening on one bank, roughly the same sort of emissions are occurring on the other bank too. So if anything starts to go off, it'll get detected by the working bank for the time being. Should I take a chance on this line of logic?

Yousuf Khan