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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 08-28-2013, 11:40 AM
AH673000 AH673000 is offline
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Mein Auto: 1997 BMW 528i
P0420 ..... Low Cat efficiency code

'97 528i with 5spd and 121k ..... Original Cats and O2 sensors ....

I get this check engine light every so often .

Today I went in for my annual Delaware SMOG and safety check. The State runs the facility and have good equipment to do a tail pipe test. Seems my car has very low emissions and passed easily .

So , question is..... Weak Cat or Weak O2 sensor?

Thx


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  #2  
Old 08-28-2013, 12:34 PM
pshovest pshovest is online now
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Tail pipe test? When I get my '98, '00 and '01 Bimmers inspected, they only hook up to OBD2 port.
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  #3  
Old 08-28-2013, 02:03 PM
AH673000 AH673000 is offline
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Mein Auto: 1997 BMW 528i
P0420 ..... Low Cat efficiency code

Interesting.... I got mine done in Georgetown this morning..... Emisions testing vis tail pipe test..... Maybe you are in the Wilmington area and need to comply with stricter emissions standards . What DE test station did you go to?


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  #4  
Old 08-28-2013, 03:17 PM
pshovest pshovest is online now
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I use both both DMV locations in NCC and the both use the OBD2 port check. Was your CEL on? Maybe the Georgetown DMV's OBD2 system is down. I think an actual measurement is a more severe test and it certainly takes longer. Was this an idle plus 2500 rpm test or is axle on a dyno?
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  #5  
Old 08-28-2013, 03:33 PM
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540 M-Sport 540 M-Sport is offline
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Quote:
Originally Posted by AH673000 View Post
'97 528i with 5spd and 121k ..... Original Cats and O2 sensors ....

I get this check engine light every so often .

Today I went in for my annual Delaware SMOG and safety check. The State runs the facility and have good equipment to do a tail pipe test. Seems my car has very low emissions and passed easily .

So , question is..... Weak Cat or Weak O2 sensor?

Thx


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I would suspect a weak catalyst. The way to know for certain, is to hook your car up through the OBDII port and using some software, you can read and graph what the post catalyst O2 sensor is reading/displaying.

It is possible the post catalyst O2 sensor is failing and a new one could eliminate the SES light.

That you can still pass a tail pipe test is not surprising...the Motronic as used on some model cars can be set up to be very (overly) sensitive. The E39 certainly falls into that category. Guys here have installed high quality, aftermarket metal matrix catalysts and get SES lights for low catalyst efficiency, yet can pass a tail pipe test.

As long as that light is on, you typically fail. If light is off, but you have "not ready" for the status of any sensor, and your car is older than a 2005, you can typically do the tail pipe test in most states. If newer than 2005, you are NOT allowed to do a tail pipe test.

If the car runs fine, the cat is not plugged, the easiest work around is a O2 sensor extender purchased off Ebay or Amazon.
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Last edited by 540 M-Sport; 08-28-2013 at 07:55 PM.
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  #6  
Old 08-28-2013, 04:16 PM
AH673000 AH673000 is offline
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Mein Auto: 1997 BMW 528i
P0420 ..... Low Cat efficiency code

Thanks for the feedback .

My CEL was not on when I tested put ok today . I am good for two more years now . The emissions tech said the results were very good for a 1997 car. I'll try a new sensor and if that fails I'll buy the extender . Still getting very good mpgs ( 22-31) and have good power .

Thx again.


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  #7  
Old 08-28-2013, 04:26 PM
Burning2nd Burning2nd is online now
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you guys are going backwards here...

Its low emissions... meaning the cats are doing more then they are suppose to

your probably coming in to a lean scenario shortly... except your o2s are doing there jobs.. and monitoring your cat pre and post comparison

try running regular octain for a while..
but you really dont have a problem
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Last edited by Burning2nd; 08-28-2013 at 04:29 PM.
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  #8  
Old 08-28-2013, 04:28 PM
Burning2nd Burning2nd is online now
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Quote:
Originally Posted by 540 M-Sport View Post

As long as that light is on, you typically fail.
iF THE light is on.. you will fail..

pa uses the same regulations as every state except cali
those guys over there think everything causes cancer

i have my emissions license
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Old 08-28-2013, 08:00 PM
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540 M-Sport 540 M-Sport is offline
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Last edited by 540 M-Sport; 08-28-2013 at 08:14 PM.
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  #10  
Old 08-28-2013, 08:12 PM
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540 M-Sport 540 M-Sport is offline
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  #11  
Old 08-28-2013, 08:18 PM
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540 M-Sport 540 M-Sport is offline
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Quote:
Originally Posted by Burning2nd View Post
you guys are going backwards here...

Its low emissions... meaning the cats are doing more then they are suppose to

your probably coming in to a lean scenario shortly... except your o2s are doing there jobs.. and monitoring your cat pre and post comparison

try running regular octain for a while..
but you really dont have a problem
I understand what you are saying, but some cars will pass a tail pipe test with flying colors and still throw a CEL/SES light for "low catalyst efficiency". I've seen and discussed this with both BMW and Ferrari techs before. The issue is the Motronic is set from the factory on some cars with very tight parameters. The car will throw the light with anything other than the OEM catalyst, in good working condition. If the cat is older, and just starting to degrade, or use an aftermarket catalyst, and it may throw the light, even though the car can still easily pass a tail pipe test. I just didn't believe this until I discussed it with these senior techs.
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  #12  
Old 08-29-2013, 02:41 AM
Burning2nd Burning2nd is online now
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Yeah but low catalyst efficiency is not the same as what he has, low emissions Is like High catalyst efficiency

Well... It would throw the CEl.. If the RAnge of the 02's was out of the spec... Normally its between .05-.09 Milli volts, Now if you know electrical thats like nothing....
you put your finger on that and it would jump 2-3 volts early just by the oms of your body
doesnt mean that its not working...

The programing would go in to a default status... Like windows safe mode
Pre heated o2's work off the heat of them selfs..

The heat generates a slight voltage, which once the o2's are in closed loop.. the program starts monitoring the voltage... off the top of my head im not sure if as the voltage goes down or up which way represents high or low efficiency
But literately this is the same on every car out there
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  #13  
Old 08-29-2013, 02:44 AM
Burning2nd Burning2nd is online now
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Oh no... ive mis read this all... I didnt see that you said po0420

catalyst system efficiency BELOW threshold Bank 1

Ignore everything i said.....

Your cats are on there way.. sorry for the mix up..
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  #14  
Old 08-29-2013, 10:58 AM
Ken@BavAuto Ken@BavAuto is offline
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Or the car might just be running lean. P0420 and P0430 codes can pop up from vacuum leaks too. We've had a few customers replace cats because of these codes and a month later the code comes back. Never hurts to have a shop check the fuel trim and see where its at before putting cats on.
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  #15  
Old 08-29-2013, 06:16 PM
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dtadrian dtadrian is offline
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Mein Auto: 1999 BMW 528i T Wagon
P0420 ..... Low Cat efficiency code

Most of the time is the post cat o2sensors are lazy and set off MIL. At least this was the case when I was a honda tech.


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