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Old 06-15-2013, 11:34 AM   #1
Dino1394
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Unhappy cat efficiency

Hey guys my car has been throwing a po420 code for a while.

Before I went an ordered the sensors I switched connectors of both o2 and the code did move to the other sides.

This lead me to believe it was just the sensor that needed to be replaced so I ordered them both. Now after replacing both sensors I am now getting a cat efficiency code for both sides.

Can anyone give me some in out of what's going on? I ordered the sensors from eBay but using the part numbers from real OEM. They were the ntk brand that I saw on the advance auto website using the same PN. They were direct plug and play so no splicing anything.

Its an 04 330xi for the mobile users who can't see my mein auto from the app.

I already failed inspection twice and I have a month left till I have to reinspect again
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Old 06-15-2013, 12:41 PM   #2
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This is a common problem with BMW and all other manufacturers in the industry.

Many times there is a minor problem, RARELY is the problem actually with the catalytic converter(s). Do not even think about replacing them at this point.

P0420 can be caused either by exhaust leaks, even very tiny ones and/or a problem with the DME software and the test window and parameters are too narrow. Many manufacturers have DME/CPU flash updates to resolve these issues.

But first lets take about exhaust leaks, even something as tiny and simple as O2 bung weld cracks, hairline cracks around where the O2 sensor threads in can cause this problem. These hairline cracks are hard to see, usually you will see blackening around the welds from exhaust gases escaping from the cracks.

Also any other post Catalytic converter exhaust leak can cause issues. Exhaust manifold to main exhaust connection or resonator connections can be the issue. Many times on manual transmission cars people cheat and cut the exhaust to perform a clutch change and use slip on exhaust pipe couplers that leak like crazy.

As for your inspection you likely can get by and get the car inspected with this issue if you manage it. Most P0420 codes only get triggered when driving at highway speeds and usually occur under long decel or coasting with very light throttle on flat or downhill slopes.

You should be able to clear the code, drive the car 1-2 days, get all the emission readiness monitors to clear, then get the car inspected. Additionally check with your state, many inspections can be preformed with 1 or 2 emission readiness codes not clear as long at the CEL is not lit at the time of inspection.

So I would focus on your inspection and not the code for now.

Search around and I would likely guess there may also be a DME update to also resolve this problem if it is a common/phantom problem with your year and model.

Good luck and report back.
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Old 06-15-2013, 04:40 PM   #3
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Off brand O2 maybe? Wasn't oem Bosch?
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Old 06-15-2013, 07:06 PM   #4
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Re: cat efficiency

Correct. I will like to blame first and foremost for the aftermarket sensors. All the vets here would agree that when it comes to sensors or electrical things, you MUST go oem. Anything else is inviting trouble. We can continue to speculate about other possibilities but not until those are switched out for oem ones, I can not help you

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Old 06-15-2013, 07:10 PM   #5
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I doubt it is the sensors, he swapped the originals and the problem did not follow the sensor.

Then he installed new sensors, he still has issues.
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Old 06-15-2013, 07:16 PM   #6
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Re: cat efficiency

Reexamine what he said

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Old 06-15-2013, 07:50 PM   #7
Dino1394
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Re: cat efficiency

Quote:
Originally Posted by NumbaOneNewb View Post
Correct. I will like to blame first and foremost for the aftermarket sensors. All the vets here would agree that when it comes to sensors or electrical things, you MUST go oem. Anything else is inviting trouble. We can continue to speculate about other possibilities but not until those are switched out for oem ones, I can not help you

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I was under the impression NTK was oem since it was the same PN as shown on realoem

I have to look into that






Quote:
Originally Posted by jfoj View Post
I doubt it is the sensors, he swapped the originals and the problem did not follow the sensor.

Then he installed new sensors, he still has issues.
No, the problem did follow the sensor when switching (420 then turned into 430).

I have to double check who makes the sensors for bmw

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Old 06-15-2013, 08:03 PM   #8
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Quote:
Originally Posted by NumbaOneNewb View Post
Reexamine what he said
Yep, I made a mistake, swore I saw a "not" in his original statement, however, he also swapped the wiring and not the sensors, this brings up a whole different set of issues, you need to move the sensor, not the wiring as there is a bit more to this than many think.

I do stick with Bosch sensors, usually can get them from Amazon for around $50 unless they are wideband (not usually used for post Cats).

Again, how quickly does your car trigger the Cat Inefficiency codes?

Assume codes get triggered while highway cruising?
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Old 06-15-2013, 08:38 PM   #9
Dino1394
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Re: cat efficiency

Quote:
Originally Posted by jfoj View Post
Yep, I made a mistake, swore I saw a "not" in his original statement, however, he also swapped the wiring and not the sensors, this brings up a whole different set of issues, you need to move the sensor, not the wiring as there is a bit more to this than many think.

I do stick with Bosch sensors, usually can get them from Amazon for around $50 unless they are wideband (not usually used for post Cats).

Again, how quickly does your car trigger the Cat Inefficiency codes?

Assume codes get triggered while highway cruising?
Damn I was wrong about brands then.

The light triggers once the catalyst monitor becomes ready.

I noticed it was a pending code yesterday after taking it on the highway to quicken the monitor readiness

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Old 06-16-2013, 07:36 AM   #10
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cat efficiency

On the keep it simple, most obvious observation....

Did you switch the wiring back to original positions when you put in the new sensors?




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Old 06-16-2013, 08:43 AM   #11
Dino1394
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Re: cat efficiency

Quote:
Originally Posted by JimC-NH View Post
On the keep it simple, most obvious observation....

Did you switch the wiring back to original positions when you put in the new sensors?




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Yeah I did. I switched em back after I saw the code went to the other before finally ordering sensors.

I find it weird the car would really reject the sensors like that.

As for a dme update im 99% it was never updated (since the nav wasnt updated neither till i did it)


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Old 06-16-2013, 09:16 AM   #12
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My experience with p0420 is this.
The post cat o2 readings should switch slowly between rich an lean indicating a properly functioning catalytic converter.
When these readings start switching rapidly (like pre-cat o2's) this code sets.
I can't remember ever seeing an o2 sensor fail this way (switching too rapidly).
Exhaust leaks can cause this. Otherwise I'd suspect the cat.
Oh yeah, DME update too.
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Old 06-16-2013, 09:37 AM   #13
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It sounds like you are on the right road, no pun intended.

You have to be sure the post CAT sensor for Bank1 is connected to the right connector else the system will be unstable. I believe you can very easily plug the Bank2 sensor into the Bank1 connector, and vice versa, and this will confuse the computer.

If you got the P0420 to turn into a P0430, then you have a bad sensor.
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Old 06-16-2013, 05:32 PM   #14
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Gotta rule out exhaust leak as well.

Time to get Torque Pro and start logging the O2 sensor(s) Voltage, this may likely give you a better idea as to what is going on. The O2 Voltage signature between banks and then swapping sensors and comparing the signature will quickly rule out sensor vs car issues.

Keep your original sensors, suggest you put the "good" original sensor back in the "bad" side of the exhaust. This could help you verify if your new sensors for some reason are not playing well.

P0420/P0430 codes are a pain in the backside and are not just an E46 or BMW issue, they plague many manufacturers.

Believe it or not, it is also possible that flakey cam sensor(s) and/or VANOS performance can cause issues as well.

Also manual transmission cars tend to have more issues as well due to more engine braking.

Is this car an automatic or manual transmission car?
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Old 06-16-2013, 08:31 PM   #15
Dino1394
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Re: cat efficiency

Thanks for all the responses everyone.

Im gonna try updating my DME soon. Since ive noticed sometimes the car feels like it bogs down at 2k when taking off

Should I try the fouler o2 trick as well?

I believe I plugged them in the right banks. Ill double check.

I never thought of buying torque pro. Has a lot of cool features. I just placed an order for the adapter to try it out.


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Old 06-17-2013, 03:50 PM   #16
Dino1394
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Update**

I tried to install the foulers but I dont have any bits big enough to drill out a hole big enough for the o2s, so I said screw it and just updated my dme

after updating I had a pending code P1515 (something about the idle speed?) I just cleared it once it threw the light a couple minutes later, since it'll come back if something is infact broken/not working

But the car's response felt better when hitting the gas. I have yet to drive it though

I connected the car to inpa and checked the voltages of the post o2s they were constant 0.40-0.43v. depending on if I revved the car up or not The pre cat o2s were doing whatever they do.

How does this sound to you guys?
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Old 06-19-2013, 10:49 AM   #17
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The only time I've seen a cat eff code is after getting O2 adaptation limit codes, searching for leaks and not finding any and right before unplugged the MAF and then changed the MAF. No more code!
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Old 06-19-2013, 04:55 PM   #18
Dino1394
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Re: cat efficiency

Readings I took today from torque pro.

Something doesn't seem right no?

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Old 06-19-2013, 09:13 PM   #19
Dino1394
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o2 readings from inpa, i think the cats are gone


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Old 08-08-2013, 04:00 PM   #20
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My wife has both P0420 and P0430 so I will need to figure out what the issue is as well. I will probably unplug and reseat the o2 sensors at the connection and check for exhaust leaks. Then if that does not solve the issue or help me identify it, what is next, replace post cat O2's? She does have 175K miles on the original O2's.
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