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Old 04-16-2014, 04:33 PM   #1
Ron ///Man
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Failing OBD2 Emissions Tests - Need Experts!

Need your help guys. Subject is 2002 M3 which is failing NY State OBD2 monitor checks with "O2 Sensor Not Ready" and "O2 Heater Not Ready".
- CEL is not on.
- Drove the car over 700 miles since CEL was cleared after VANOS repair.

Made sure I went thru all OBD2 Drive scenario's to trigger monitor's at least twice.

So far, the only thing I found was a loose O2 sensor. I looked at O2 sensor outputs with a scan tool I have and all fore and aft sensor's seem equal in voltage output. Secondary fuel trim seems very high though. Car does smell a tad rich to me as well.

The 800 lb gorilla in the room is that the car has aftermarket SS headers, so forward cats aren't in the picture anymore. My hunch is the O2's are looking for the hotter exhaust temps after the cats to heat them up properly? I sincerely hope this is not the case as I bought the car with the headers installed and don't have the stock ones to put back on.....

What's the popular opinion?? Any help is greatly appreciated!

Ron
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Old 04-16-2014, 05:58 PM   #2
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missing cats is pretty sure way of failing emissions testing.

Last edited by jcns; 04-16-2014 at 05:58 PM.
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Old 04-16-2014, 06:26 PM   #3
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Are O2 sensors(pre cat) hooked up at all? Like did it have o2 bungs installed? Or are they just disconnected?

I had to deal with this on my old 5 series. I'll check back later. Several options.
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Old 04-16-2014, 06:29 PM   #4
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Try replacing the O2 sensor. No experts needed here.
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Old 04-16-2014, 06:44 PM   #5
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Originally Posted by wapner View Post
Are O2 sensors(pre cat) hooked up at all? Like did it have o2 bungs installed? Or are they just disconnected?

I had to deal with this on my old 5 series. I'll check back later. Several options.
Headers are Fabspeed, so good stuff. They have bungs for all O2 Sensor's which are installed and hooked up. If they weren't hooked up, I'm sure CEL would set, no? I'm just wondering if the O2's need the hot post-cat exhaust to put them into ready state? CEL is NOT on....


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Try replacing the O2 sensor. No experts needed here.
Trying to avoid the expense of changing 4 O2's w/o being sure it will fix the problem. The output voltages look identical L and R, Fore and Aft, so my conclusion is that they are probably all good, or all are bad. Car runs too good for all to be bad, but that means nothing in the world of EFI control.
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Old 04-16-2014, 06:48 PM   #6
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How about the cat monitor?

Is there a tailpipe emission test in NY?
I don't see how you can pass it without cats, even if the O2 monitors clear.
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Old 04-16-2014, 06:52 PM   #7
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How about the cat monitor?

Is there a tailpipe emission test in NY?
I don't see how you can pass it without cats, even if the O2 monitors clear.
Cat monitor must be in 'ready' state as only the O2 and O2 Heater aren't. They didn't give me a copy of the report, so I can't check, but they did write down "O2 Sensor and O2 Heater Not ready". There is no tailpipe emission test where I live in NY State, only OBD2 readout of fault codes and monitor readiness. NY State will pass a car with one monitor not ready, but I have two...
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Old 04-16-2014, 07:44 PM   #8
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You can try heating each O2 with a propane torch till tip glows orange then dip in water (controversial I know) lotsa youtubes on it. Repeat drive cycle, and see if that helped.
Go to junk yard, or post a WTB on original cats and reinstall and test that way, pass then put headers back on. Not sure how NY system is(works in IL) sell car to family member, emissions gets recycled for a year(buys ya time to sort it out), some counties here don't even require emmisions.

I know ya said ya did, but you're sure you followed the readiness test exactly right? Reason I ask is I don't think you could have a bad O2 w/o throwin a code.
I battled this for years swapping headers on and off, bouncing title around my family, it's a real pain the ass man. I feel for ya.
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Old 04-16-2014, 07:47 PM   #9
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Just in case. That step between 40-60 mph w/o going over 3,000 rpm or touching brake is tough to pull off, I always had to do in middle of the night.
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Old 04-16-2014, 08:04 PM   #10
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Originally Posted by Ron ///Man View Post
Cat monitor must be in 'ready' state as only the O2 and O2 Heater aren't. They didn't give me a copy of the report, so I can't check, but they did write down "O2 Sensor and O2 Heater Not ready". There is no tailpipe emission test where I live in NY State, only OBD2 readout of fault codes and monitor readiness. NY State will pass a car with one monitor not ready, but I have two...
Check the wiring to the sensors, if there is 12V at the connectors, just replace the O2 sensors.
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Old 04-16-2014, 08:20 PM   #11
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Just in case. That step between 40-60 mph w/o going over 3,000 rpm or touching brake is tough to pull off, I always had to do in middle of the night.
Yea, I did the test a few times. It's tough to do with traffic, but I found a route. Pretty sure I was successful on all of them. I surely did what the sheet says to do exactly as it says.
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Old 04-16-2014, 08:22 PM   #12
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Check the wiring to the sensors, if there is 12V at the connectors, just replace the O2 sensors.
Will check for 12V tomorrow. Perhaps a heater is missing 12V? That would be cool and easy to fix. If not, I guess I may have to spend the $$$ for four O2's.... Car has 73K and from research, I think they start acting up around 100K.
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Old 04-16-2014, 08:37 PM   #13
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Yea, I did the test a few times. It's tough to do with traffic, but I found a route. Pretty sure I was successful on all of them. I surely did what the sheet says to do exactly as it says.
Yeah its a bear to pull off. Especially the tail end coasting to a stop w/o hitting brake and then idling. Takes forever to coast to stop, I started using curbs to slow me down.

Take a look at some wreckers for used o2's. Ebay has em used to. Sucks to have to spend $400 for something that might not cure.
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Old 04-16-2014, 08:42 PM   #14
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http://www.ebay.com/itm/BMW-E39-540i...5f548a&vxp=mtr

This guy has 2 pres for $29, might be worth a roll of the dice
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