Oxygen Sensor

[LilBimmer]

My "Check Engine" light has been on for a week so I just took it into this local shop that says they specialize in German makes. Thay told that the code is calling for a new "front " oxygen sensor. They say there are two, one front and one rear. I didn't realize that there were two because the service manual calls for a new oxygen sensor every 100K miles.

I just want to make sure that what they're telling me is true and these guys are legit. Does this sound about right? Is this something that can be replaced by me?

I have a 1997 Active with less than 50K. Any input would be helpful!

[Teno]

Same problem happen to me! My 318TI has 70,000 miles. Any idea on the cost of this repair? Can a local mechanic do it? Or does it need to go to the dealer? Thanks! Joan

[J!m]

There are two sensors on the ti (don't feel bad: the M3 has FOUR :shock: ).

the 'front' sensor as he calls it is in the exhaust manifold, probably easiest to get from underneath. the 'rear' is in the head pipe, further down stream, about at the centerline of the front and rear wheels.

Basically, just un-plug it, unscrew it, put hi-temp. never-seez (typically copper-type) on the threads of the new one, screw it in, plug it in, have the fault codes re-set.

Not brain surgery, but sometimes they can be a bitch to remove. If your's is not cooperating, spray with WD-40 (or whatever you prefer) and let is soak for a few hours. Keep it wet with the penetrant. Then attack it again.

[LilBimmer]

Thanks J!M. I'll give it a shot.

[mrnine]

A couple oxygen sensor questions:

1) Is it really helpful to have the tool for removal? Can it be done reasonably without it (using wd-40 or other penetrating oil as above)? Will a normal wrench work? I've checked 'em out, but not closely.

2) I found a deal for $182 for both. (http://www.eap4parts.com) That seems reasonable when I comparison shop. Cheaper than bavauto or anywhere else. Unless anyone else can suggest a better deal, I'll assume that's pretty good.

[J!m]

It depends on how siezed the ba$tard is...

Sometimes an open-end wrench is all you need, other times, God himself is found wanting.

A box-end six-point wrench is probably the best thing, IF you can get it in there. After you un-plug it, slip the wrench on. Next may be a flare-nut crow's foot. I have not needed the 'special' tool (6-point socket with slot in the side) yet myself, I can usually find another tool/way to do it.

[simo2k]

hi when you say there are two oxygen sensors in the exhaust one is usually pre cat and one after cat there is only one pre cat sensor on my 98 ti but like jim says a usual 22mm open end spanner should shift it
quit easy to do

just a question for you guys in the states what do you think of mac tools over snap-on, im a technician here in the uk and buy a bit of both but not much difference to me just that mac is abit cheaper ?

[J!m]

I'm a bit biased, as I am a third generation Snap-On tool user, but I have tried them all.

I have the most trouble breaking Snap-On tools, which is why I choose them, but I break them all. I actually have some Snap-On tools that were my Grandfather's, still in use!!

I work in my own shop, so the truck does not visit me, I go to the truck. Snap-On is convenient for me as well, since he lives a few miles away. (I get a slight discount from my guy since he sold to my dad for years as well)

I also have a Matco tool distributor at an equal distance from my house, but those tools are REALLY crap, and I refuse to use them. The few Mac tools I have left seem fine, but I did not like the sharpish edges on the wrenches, which get uncomfortable after a while (I have purged all the Mac wrenches from my tool collection for this reason).

I WILL NOT buy a Snap-On tool box. They are nice, but HORRIBLY overpriced. I suggest Lista for tool storage, as they make the best storage solutions (IMO) bar none.

[simo2k]

i must agree with you on the spanners and storage boxes i have a mac storage box at the mo it cost me 1200 squid not as well built as snap-on but its just for storage. also i bet snap-on and mac tools take an advantage in this country cos we get taxed and vat to the max i get paid £450 a week and mot cars as well and get bloody taxed £130 of it

mind you i suppose it beats living in a dodgy country..

ps: have you watched that fahrenheit 9/11 yet, well dodgy if the film is authentic.

[J!m]

Have not seen that flick yet...

See if you can get Lista boxes over there. They look european, but are American made. In spite of this inherent flaw, they are the $hit.

Construction is better quality with heavier material, drawer dividers are easily installed, drawers are modular, so you can arrange them any way you want, custom colors are no problem, etc.

I had a small one where I used to work, and it worked well, even after being hit by a fork-lift. I don't think any other box made will withstand that abuse...

[bimmerboi318]

if im correct, 95 ti's (OBD-1) have one, pre cat O2 sensor. the OBD-2 96 and later ti's have 2. one pre cat sensor and one after the cat for the catalyst efficiency monitor. im only assuming the 96 and later ti's have 2, as i've only been under my ti which is a 95. but im pretty sure that most OBD-2 systems use sensors before and after the cat.

yes they can be a real pain (major understatement) to get out. seeing mine though, it doesnt seem like space will be an issue, so a regular wrench SHOULD be ok. on the topic of tools, snap-on makes a really nice O2 sensor wrench that has a pivoting head and everything, for a mere 80 bucks or so :lol: (sarcasm).

i usually deal with snap-on since the truck stops by every monday. and i did buy a nice box from him that was part of a scratch and dent sale. unnoticable dent and the box was half price. but otherwise, yeah, extremely overpriced.

[simo2k]

the only reason i said that my 98 ti has only got 1 pre cat o2 sensor is cause i had to replace my cat not so long ago as the ceramic broke up inside and rattling. not bad though as it is only the first real repair i have had to do since owning the car. gotta say i love bmw cars lol..

[l3etamax]

How do you go about doing a fault codes re-set? Do you have to go to a shop? :_paper:

[aceyx]

autozone and similar stores generally have a free tool rental policy. while not the best stuff, generally does the job and beats paying for tools you barely use (pullers, etc).

other brands of tools i've liked is facom (supplier to ferrari race teams) and stanley-proto.


betamax; if somebody near you has a code reader it can usually do a reset as well.

[Buttercup]

I have 2 questions...

1. When the oxygen sensor gets replaced at 100,000 miles, does that mean both of them should be replaced? (I have a 96, so I have 2). If not, which one?

2. To do a fault codes reset, is that the same as resetting the codes after doing an oil change?

[mrnine]

Wow!

So my Oxygen sensor error finally came up and I installed the O2 sensor that I bought months ago knowing it would go out soon enough. The install was a piece of cake after some penetrating oil.

I suppose it could be my imagination (and if it's not, I'm sure it's marginal) but it certainly seems like there is noticably more consistent power throughout now. Definitely runs more smoothly. I'll be keeping my eye on mileage over the next few weeks and will hopefully see improvement there as well! (Unless of course I am forced to continue to "test" this "increased power.") :)

Re: Buttercup

1. When the oxygen sensor gets replaced at 100,000 miles, does that mean both of them should be replaced? (I have a 96, so I have 2). If not, which one?

A: My o2 sensor fault code just came up on my '98 at 111k. My Peake reset tool told me that it was the sensor before the catalyst, which seems to be the one to most commonly fail first, from what I've read.

2. To do a fault codes reset, is that the same as resetting the codes after doing an oil change?

A: The fault code reset is different than an oil reset. I decided a) my car was up enough in the miles, b) I'd like to keep it for a long time and, c) I'm far enough from a BMW dealer that it made sense to drop $130 on a Peake reset tool. I've really appreciated having it already and should get years of use out of it. But then I'm a gadget freak so that could just be rationalization. Whee!

-R

[aceyx]

an o2 sensor that is new will read the outgoing air/fuel mixture better, giving a cleaner burn in the cylinders. when dirty, it thinks there is too much, so it runs a little on the lean side.

postcat o2 sensor will do the same thing, but generally takes longer to fail since it's after the cat (whose purpose is to burn off unburnt fuel, so it takes longer to foul).


i noticed the same increase after the o2 harness recall, which i actually wasn't aware was being done at the time. so you're not alone in thinking there's a boost, or we're both imagining things.

[pdxmotorhead]

If you can't get the sensor out gently,,,,

Simply break off the sensor. The part above the nut is usually
light sheet metal over ceramic. Cut off the wires at the sensor,
(NOT ABOVE THE CONNECTOR!!! ; :icon_eek:
put the box end over it and snap it off. Then a standard or deep
well socket will remove it. The special socket for O2 sensors sold
by most suppliers will put one in fine but will often open up and
slip on a really seised in sensor. It also helps if you warm up the
engine just till you don't want to hang on to the pipe but the sensor
is still cold.

I havn't changed mine yet on the BMW but this technique has worked
on a lot of other vehicles for me.

Dave

[KdCass]

I changed my precat o2 sensor today @ 116k. I too feel a increase in resposiveness and acceleration. :biggrin:

The O2 sensoers are easy to pull, well with decent tools. The tools you need to EASILY pull the sensors are 'free' rental for ulimited time. I broke my ratchet trying at first. A trip to autozone for a new one and a breaker bar. Breaker bar rules I broke them both loose with minimal effort first try with a little wd40. I was working my but off when i broke the ratchet.

Originally I thought it was the post cat sensor (according to free AZ code pull). Then after i pulled it I realized the one I bought from Autozone was the precat :rolleyes: Dont know it I missunderstood or he screwd up :_punch:

I noticed the precat was the original sensor so I changed it. I followed the Haynes manual the first step is to pull the negative battery cable so I did CEL is gone. So why do I need to reset anyting?

-Dave