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Old 12-27-2012, 04:41 AM   #1
TArse
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o2 sensor question.

my check engine light has been on for awhile now. I had a pretty bad tear in my LIB and I was getting lean codes on all my post cats.

I replaced the boot and reset the CEL. I have another CEL, I red it with my peake tool and got table 19 eb (pre cat fuel trim system #1-#3)

it's only one sensor, is it possible I still have a leak or is it a bad o2?
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Old 12-27-2012, 07:43 AM   #2
jfoj
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Air leak, suggest you read the first link below in my signature.

Get the cheap and easy stuff sorted first.

Rarely the sensors, but fresh O2 sensors never hurt, they just usually cause more CEL as they are more sensitive!!

Also check the 2nd link in my signature as well, fuel filter and pumps are really PM at his age as well.

I laugh at all the people that spend $$$ on a MAF as the first part replaced (it is the easiest part to replaced), then fail to address all the items that really need to be replaced. You could change your fuel pump, filter and most of the rubber parts for the price of a MAF and actually correct most of the problems these cars have at this age.
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Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

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Old 01-09-2013, 10:02 AM   #3
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did some digging in the engine bay over the weekend. I couldn't find any obvious cracks or dry rot.

it's just weird to me that is only on the 1-3 precat and not the other. in my past experiences a leak threw a 4 sensors.

another thing. the idle is not erratic and the cel comes in at highway speeds.
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Old 01-09-2013, 10:53 AM   #4
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did some digging in the engine bay over the weekend. I couldn't find any obvious cracks or dry rot.

it's just weird to me that is only on the 1-3 precat and not the other. in my past experiences a leak threw a 4 sensors.

another thing. the idle is not erratic and the cel comes in at highway speeds.
Not if its the bank 1 pre cat O2 sensor that's playing up. Normally teh car runs like sh*te if a pre cat O2 sensor goes though. Maybe its just on the turn and ready to dump on you.
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Old 01-09-2013, 09:51 PM   #5
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Not if its the bank 1 pre cat O2 sensor that's playing up. Normally teh car runs like sh*te if a pre cat O2 sensor goes though. Maybe its just on the turn and ready to dump on you.
is there a way to know for sure?
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Old 01-10-2013, 04:14 PM   #6
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I have an 04 330 sport and the light came on the other day had a mate read it and said it came up with bank 1 cat Efficiency the sensor after the cat was not the same as the other one on the read out is it the down Stream ? It has gone out a few times but come back on. Also am I right in thinking my car only has two cats the ones on the engine ?
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Old 01-14-2013, 10:36 AM   #7
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I have an 04 330 sport and the light came on the other day had a mate read it and said it came up with bank 1 cat Efficiency the sensor after the cat was not the same as the other one on the read out is it the down Stream ? It has gone out a few times but come back on. Also am I right in thinking my car only has two cats the ones on the engine ?
huh?



also i be digging in the bay later today. will report back. I hope I find something small.
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Old 01-14-2013, 10:46 AM   #8
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is there a way to know for sure?
Not really. Not with the unit in the car and if you are going to go to the trouble of removing it you might as well replace it. As for the post cat O2 sensors they don't have any feedback impact on fuel mix the way that the pre cats do although they will lead to an emmission test failure if they indicate bad emmissions.
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Old 01-14-2013, 12:40 PM   #9
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Not really. Not with the unit in the car and if you are going to go to the trouble of removing it you might as well replace it. As for the post cat O2 sensors they don't have any feedback impact on fuel mix the way that the pre cats do although they will lead to an emmission test failure if they indicate bad emmissions.
well today I'm going to swap the precats an if the code comes up on the other set of cylinders ill know. I have headers so it'll be an easy task.
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Old 01-14-2013, 01:04 PM   #10
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well today I'm going to swap the precats an if the code comes up on the other set of cylinders ill know. I have headers so it'll be an easy task.
Just to clarify. The pre cat O2 sensors are the ones between the engine and the cat on each header. So there is one for the header for cyls 1 - 3 (bank 1) and one for the header for cyls 3 - 4 (bank 2). So if you are changing the pre cats then you are changing the cats for both banks ie: all six cylinders. Ok?
The other two O2 sensors are the post cat sensors. There is one after the cat on wach header.
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Old 01-14-2013, 01:11 PM   #11
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Just to clarify. The pre cat O2 sensors are the ones between the engine and the cat on each header. So there is one for the header for cyls 1 - 3 (bank 1) and one for the header for cyls 3 - 4 (bank 2). So if you are changing the pre cats then you are changing the cats for both banks ie: all six cylinders. Ok?
The other two O2 sensors are the post cat sensors. There is one after the cat on wach header.
you lost me man.


-there are pre cat o2s (the ones between the engine and cats. these adjust fuel mixtures)

-there are post cat o2s (after the cats. these let you know if your cats are working properly)

I'm just swapping the the pre cats. bank 1 (1-3) to bank 2 (4-6). if the code jumps to the other set of cylinders I will know the problem is the o2.


I'm really not sure what you were trying to say/ask in that post.
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Old 01-14-2013, 01:13 PM   #12
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So if you are changing the pre cats then you are changing the cats for both banks ie: all six cylinders. Ok?
this is where you lost me.
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Old 01-14-2013, 01:18 PM   #13
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you lost me man.


-there are pre cat o2s (the ones between the engine and cats. these adjust fuel mixtures)

-there are post cat o2s (after the cats. these let you know if your cats are working properly)

I'm just swapping the the pre cats. bank 1 (1-3) to bank 2 (4-6). if the code jumps to the other set of cylinders I will know the problem is the o2.


I'm really not sure what you were trying to say/ask in that post.
Sorry man. I read SWAP in your comment and thought REPLACE. But you are actually going to swap them over and see if the error moves. I get it now. Sometimes the two words are interchangeable.
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Old 01-14-2013, 01:20 PM   #14
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Sorry man. I read SWAP in your comment and thought REPLACE. But you are actually going to swap them over and see if the error moves. I get it now. Sometimes the two words are interchangeable.
it's all good, I see where the confusion came in.

I figure I can do this in the mean time as I'd rather not just go spend ~$150 on a sensor I don't "need"
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Old 01-14-2013, 05:25 PM   #15
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no luck. I don't have a wrench that fits the o2
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Old 01-15-2013, 02:49 AM   #16
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no luck. I don't have a wrench that fits the o2
I was going to mention that but thought you had it in hand. You can buy a special socket looks like this.

http://www.amazon.co.uk/dp/B000MQ7XR..._df_B000MQ7XRA

Use it like this


Last edited by RayPooley; 01-15-2013 at 02:50 AM.
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Old 01-15-2013, 05:38 AM   #17
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it's all good, I see where the confusion came in.

I figure I can do this in the mean time as I'd rather not just go spend ~$150 on a sensor I don't "need"
Here is the deal, O2 sensors are like spark plugs, they are consumable and it is recommended that they be replaced at 100k miles, but this does not mean they last 100k miles and many times they can last more than 100k miles.

Front O2 sensors should be about $50 each. Get ONLY Bosch. I buy all mine on Amazon.com and usually they are about $50 each.

As for a tool, most auto parts stores will loan them to you free of charge.

If you do not have a scan tool that can read real time data, you either have to swap them, for that effort, I would replace them, or replace them.

You will likely break the vacuum line that runs around the edge of the valve cover, if it no already broken now. So plan on replacing it from the back of the engine on the drivers side to the SAP valve at the front passenger side.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 01-15-2013, 05:49 AM   #18
TArse
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Originally Posted by RayPooley View Post
I was going to mention that but thought you had it in hand. You can buy a special socket looks like this.

http://www.amazon.co.uk/dp/B000MQ7XR..._df_B000MQ7XRA

Use it like this


thanks.


Quote:
Originally Posted by jfoj View Post
Here is the deal, O2 sensors are like spark plugs, they are consumable and it is recommended that they be replaced at 100k miles, but this does not mean they last 100k miles and many times they can last more than 100k miles.

Front O2 sensors should be about $50 each. Get ONLY Bosch. I buy all mine on Amazon.com and usually they are about $50 each.

As for a tool, most auto parts stores will loan them to you free of charge.

If you do not have a scan tool that can read real time data, you either have to swap them, for that effort, I would replace them, or replace them.

You will likely break the vacuum line that runs around the edge of the valve cover, if it no already broken now. So plan on replacing it from the back of the engine on the drivers side to the SAP valve at the front passenger side.
I will go ahead and check that line today as I've had o2 sensors replaced in the past and over looked that one
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Old 01-16-2013, 11:37 AM   #19
TArse
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couldn't check anything yesterday because of rain.

but I did clear the code and it came back after 20mi.
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Old 03-22-2013, 03:47 PM   #20
TArse
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Ended up being a "crushed" o2 sensor nipple/nozzle. There is (was, ground down now) weld bead that the o2 was hitting and apparently slightly crushed the nipple causing the slits to widen letting in more oxygen.
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