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Discussion Starter #1 (Edited)
I just bought the car (2001 M5 w/ 23k mi) and it failed the CA smog test. It failed HC at 15MPH with 80ppm measured, 47PPM MAX allowed, and barely passed the 25MPH with 30PPM, 31PPM MAX allowed. I have the car tested 3 times at two different locations, and each time resulting in about the same numbers. I drove the car 30 min prior taking the car in for smog. After the 1st failure, I took the car to the BMW dealer (in San Jose) for diagnosis. They hooked up the computer and couldn't detect any fault code, but updated the software anyway. I took it in for 2nd smog test, and it failed with the same number. On the 3rd try, I changed the spark plugs and it failed as well. Prior to the smog tests, I ran a tank of premium gas w/ Chevron Techron fuel injector cleaner.
BTW, this car was imported from Germany back in 2005, so it's a German spec car. Now the dealer realizes that it's a grey market car, and refuses to work on emission issues.
Anybody here had this problem w/ low mileage cars?
Maybe German cars run different software for the DME or ECM with a slightly richer fuel/air mixture at low speed?
I can't imagine that both catalytic converters went bad at the same time especially with only 23k mi. I've read that if the cats go bad, both HC and NO would be high. But the measured numbers for NO and CO are close to zero. O2 sensors should be fine at this low mileage. I've already changed the air filters, spark plugs and engine oil.
Any idea guys?
 

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Discussion Starter #3
Thanks for the link and I read thru your post. It does seem like that the VANOS seal was the problem in your car. Did you buy the O-ring kit from drvanos.com for $115 E39 M5 Vanos ? The website has a long DIY procedure in changing the VANOS. Do you know of an easy DIY in changing the O-rings only? My car only has 23k mi but then it's a 10-yr old car, it probably doesn't hurt to change the O-rings.
Interesting that you mentioned you've tried the CRC "guarantee to pass" and that didn't work for you. I just added a can of this stuff last night, and probably it won't work. I'd already tried the Chevron stuff.
 

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. But the measured numbers for NO and CO are close to zero. O2 sensors should be fine at this low mileage. I've already changed the air filters, spark plugs and engine oil.
Any idea guys?
O2 are likely done. You should not be a zero for either Nox or CO they really should be middle to the higher part of the range. Basically extra air makes the NO and CO go up and you have high HC which also says not enough air. Conclusion would be not enough left over air or car is rich.

Likely failed O2s they get bad with age also. Then they say there is more air in the exhaust than there is so the car gets richer. Big thing here is to confirm your t-stat is working correctly. Your results are a bit different at least how you explained, To ards he had normal CO and Nox was a little low. My not very well informed guess is t-stat. If you just got the car then you may not know about the secret OBC test and test seven so here is a link to be safe.
http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/1898-gadget-freaks-ii-fun-you-never-knew-you-could-have-secret-menu.html

You could scan and post both of your reports. There is other helpful info in them.

There is one other little twist here Euro cars have the cats farther down the car, it was Cal emissions that insisted that the cats be moved closer to the motor. It is only 4" but
 

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Discussion Starter #5
Thanks for the link to the secret menu. Very cool.
The thermostat temperature is fine (t-stat if that's what you're referring to), right in the middle of the gauge.
The NO and CO numbers are not zero, but close and below average.
The master tech and the techs at the smog stations thought that the O2 and the spark plugs were fine. But I changed the plugs anyway.

What kind of scanned report are you looking for? My Peake scanner can't pickup any fault code; the dealer's software can't see any problem either. I probably should take it to a BMW indy shop and have them to run the GT1 scanner.
 

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When you got the fails did they not give you a print out?
Did these techs at the dealer do a Vanos test?
Could be like Ards then if the other gas are not to low could be EGR problem which is the exhaust valve timing. Too much exhaust gas returned = not enough air.

Couple of things do a search on t-stats, the gauge is not accurate in fact it is an idiot light that just looks like a gauge. Then monitor test 7. In other words the gauge doesn't mean much. Most "new to me" cars need stats you will see when you search. It has to do more with the temp falling and some other things. Give time for the injector cleaner to work. Don't use extra high octane for your e test. Just use what is normal for the car, sometimes 91 or even 89 yield better results as far as smog.

Last but not least I would love to have the techs try and explain to me how they know the O2 are good. They did not send them out to a lab that can actually test them so they are guessing.
 

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; the dealer's software can't see any problem either. .

"dealer" as in BMW dealer? They have all the tools to diagnose. Monitori O2 sensor outputs, make sure they are changing properly; look at AFRs; look at fuel trims; even run the vanos test.

Given that most of us do NOT have access to a GT1, we are constantly looking at strategies to get these cars fixed with a funny strategy to minimize expense and optimize our DIY...hence stuff like replacing O2s; plugs; CPS, etc- while possible not necessary, are reasonable tasks- maybe it isn't needed, but will be, and might as well eliminate it as a possibility.

Might as well change the O2s.
 

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European cars lagged WAY behind US emission standards, let alone Californian standards, and still do, AFAIK.
Cats were not required in Europe until 1993. So I wonder if the type of cats you have, or the fuelling tables in the DME, are your problem.
 

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Discussion Starter #9
The catalytic converter part# for European and US spec M5 is the same. I checked w/ the BMW dealer already.
The BMW dealer hooked their computer (not GT1, too old they said and not using that anymore) and couldn't find any fault code. The master tech didn't remove the O2 sensors or did any emission test. He said if the O2 sensors were completely dead or slow to respond, fault codes would be generated. Both the techs at the dealer and smog station said that the O2 sensors are good for 100k mi, independent of age, unless the sensors were contaminated.

Here's the result from the smog test:
15mph: HC (PPM), Max 47, AVE 4, 60 MEAS. CO (%), MAX 0.46, AVE 0.01, MEAS 0.04. NO (PPM), MAX 400, AVE 16, MEAS 0
25mph: HC (PPM), MAX 31, AVE 4, 30 MEAS. CO (%), MAX 0.43, AVE 0.01, MEAS 0.02. NO (PPM), MAX 687, AVE 18, MEAS 0

The measured NO is indeed 0.

I tried to run OBD test 7 (t-stat temperature), but message on the screen shows "LOCK:ON". I need to figure out how to unlock this test.

Yesterday as I was trying to replace the front two O2 sensors, and ended up successfully replacing the driver side. I couldn't loosen the O2 on the passenger side and stripped the nut, and made a few dents on the body of the sensor. Today I took a long 4 hr drive around the bay area (the longest drive I've ever taken on this car. I can tell you that the engine sound, power, speed and handling is intoxicating). At the end of the long drive, as I pulled the car into the drive way, the SES light came on. The Peake scanned codes show 0d (precat O2 cyl #1-4) and 90 (fuel control cyl#1-4). I wonder if it's a coincident that I'd damaged this O2 sensor or does it really take that long for the computer to pick up a faulty O2 sensor. I need to go to a shop to get this O2 replaced since I can't seem to get it loose.
 

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^^^ That "master mechanic" is a Fing moron. He is relying on only "codes" to diagnose O2?? His position is "no codes, engine is running great"??? That is really astounding.

You add the last 5 digits of your VIN, that is the 'unlock key' for the OBD display...go to test 20 with the right button, then press the left button to incremet up to [your number], then the right button and it will be unlocked.
 

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The zero on the NO emissions and the too low on CO is from bad post cat O2 sensors. Bad is to strong a word they are just lying a bit and saying there is more air than there should be. This is low mileage for them to be bad but the length of time they have been installed could be the cause. Although platinum "does not oxidize" I think it is really "platinum oxidizes very slowly" and that is the key to a O2 sensor. I would encourage you to replace all four O2 sensors and give yourself a fresh start.

Denting the case could be the key to your code. The O2 sensor reads the exhaust but it also allows air into the other side or inside and compares the the air to exhaust. You may have crushed or blocked a passage.
 

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I've never seen a post on this forum where POST cat O2 sensors made ANY difference in how a car runs or emissions levels. To my knowledge the ONLY thing they do is check the CAT condition and set a CAT code....
 

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Discussion Starter #13 (Edited)
This morning I went to an Arco gas station auto shop and asked them to loosen the O2 sensor (front, passenger side). They wanted $200 for a complete job, labor + part, and didn't want to use the part I brought in. Then I went to a Quality Tuneup shop and the owner quoted me $65 to $125 in labor, depending on how difficult the job was. He put the car on the ramp and used 3 different types of O2 sensor socket/wrench, worked on it for 20 mins and still couldn't break loose the sensor. By then the nut on the sensor was completely rounded. As a last hope, he used a channel lock and a 3-ft extension bar. And it took two guys finally broken loose the sensor. He'd never seen any O2 sensor got stuck so badly. The job was done in 30 mins, and I paid $95 for labor. The sensor was completely covered in black ash. The other front O2 sensor I took out the day before had the normal grayish burnt. Hopefully, the high HC emission was a result of this sensor. I'll drive for a few days and take it in for retest.

Here's the picture of the dead O2 sensor.
 

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I've never seen a post on this forum where POST cat O2 sensors made ANY difference in how a car runs or emissions levels. To my knowledge the ONLY thing they do is check the CAT condition and set a CAT code....
Yes I am quite aware of the unimportant role you believe the post cat sensor has. I have told you that if I put spacers between postcat sensors and the pipes that the car leans out. The only thing affected is the post cat sensor, so how does that happen if the post cat sensor does nothing. If I test the exhaust gas, with these on, I will be high in Nox. I will mail you a couple spacers and you can put them in your car and see for yourself.

I really am not going to kill myself trying to explain this I have tried without success, I may even be wrong, M5 is different. I have not said I know for a fact that it happens on a M5. If it does not, it would be the only case I am aware of that does not compare the two waveforms and I am not just talking about cars. The second O2 sensor came into being at the same time as controls on Nox emissions. I have seen other posts on this with guys trying to explain and they gave up. Some of the best posts on this were from Amp and he gave up too.

I will not say in the M5 , but in industry when we were forced to control Nox emission we put in a second O2 sensor to "monitor the gases" (see same wording) after they had been converted by the cat. When the post cat sensor sees too much air(will be high Nox) or not enough air( not enough Nox so not efficient burn) it asks for an adjustment in the air. How that adjustment is made depends on the burn process but on a car it is usually by adjusting the exhaust gas returned.

If the job of the post O2 was as simple as you say then when we throw B2 and 3 our cats really would be toast.

In all fairness no one really believed me when I suggested that the reason for VANOs on the exhaust valves was to return exhaust gas.
 

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Discussion Starter #15 (Edited)
Ard, Sailer24, Thanks for all the advice.
The car finally passed the CA emission test (barely).
HC 15MPH, 47max, 47 measured.
25MPH, 31 max, 31 measured.
It was after all a bad front O2 sensor as stated in previous posts.

The HC is still on the high side. Well, at least it's good for 2 more yrs. Maybe I should tackle the VANOS seal in the coming year.
 

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Discussion Starter #16
After seeing the last post by M55555 http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/173546-smog-results-fail-2.html, I should consider replacing the post-cat O2 sensors two yrs from now if it fails again. From all of the information I've read the post-cat O2 sensors shouldn't affect emission since the car's computer does not do any adjustment to fuel/air ratio or timing from the voltage reading of the post-cat sensors, unless the M5 development engineers were doing something w/ the post-cat sensor information and didn't let anyone know about it.
 

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After seeing the last post by M55555 http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/173546-smog-results-fail-2.html, I should consider replacing the post-cat O2 sensors two yrs from now if it fails again. From all of the information I've read the post-cat O2 sensors shouldn't affect emission since the car's computer does not do any adjustment to fuel/air ratio or timing from the voltage reading of the post-cat sensors, unless the M5 development engineers were doing something w/ the post-cat sensor information and didn't let anyone know about it.
The only thing that I changed after my first initial fail was the Post-O2 sensors, as I already replaced the Pre-O2 prior to the first test.
 

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When the post cat sensor sees too much air(will be high Nox) or not enough air( not enough Nox so not efficient burn) it asks for an adjustment in the air. How that adjustment is made depends on the burn process but on a car it is usually by adjusting the exhaust gas returned.
Sailor, this statement got me hauling out the trusty GM shop manual for my 2000 truck because it has very detailed info on all the emissions components and how they work. I wanted to see if the ECM used the post cat sensors as inputs for EGR valve operation to support your statement above. It doesn't. It only uses the throttle position sensor, MAP sensor, and coolant temp sensor.

I agree that just because GM doesn't use the post cat sensors, it doesn't prove BMW doesn't.

To the OP, congratulations on passing the infernal test!
 

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FYI...I'd been fighting rich-running for years. Three years ago barely passed. Then this year failed. Finally nailed it with that vanos thing.

The issue with running rich is that you get fuel shear and dilution of your oil...which the bearings do not like.
 

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Sailor, this statement got me hauling out the trusty GM shop manual for my 2000 truck because it has very detailed info on all the emissions components and how they work. I wanted to see if the ECM used the post cat sensors as inputs for EGR valve operation to support your statement above. It doesn't. It only uses the throttle position sensor, MAP sensor, and coolant temp sensor.

I agree that just because GM doesn't use the post cat sensors, it doesn't prove BMW doesn't.

To the OP, congratulations on passing the infernal test!
First if it was a HD 2000 truck it may not be OBDII, allot of HD trucks are not required to comply.
ALL GM CARS AND TRUCKS COMPARE POST AND PRE O2 TO SET TRIM IF OBDII. Not a think so, a know so! If you don't know that, I am not talking about this to you. Not to mention you are wrong about the EGR, settings are hidden in the trim. The three sensors you talk about are just variables that affect pulse rates of the EGR control devices.

Believe what you want, I do not care if you want to run 10 year old O2s. If you don't want to accept that the modern engine is a mixture between exhaust gas , air and fuel, fine. Explain how one O2 sensor can handle the triple mixture, and the triple threat Nox ,CO and HC. I can't wait.

You seem to be hung up because BMW says that the post cat sensors monitor cat efficiency. They do but no where in that statement does it say they do nothing about what they are monitoring. They monitor and when they find things are not right things get changed until the changes are out of range. When the DME can do no more you end up with B2,3 or if other things are lying you may end up with a fuel code.
 
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