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Thread: Getting codes 29F4 29F5 - O2 or Cats?

  1. #1
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    Getting codes 29F4 29F5 - O2 or Cats?

    Not sure if I should replace the cats or O2 sensors. I’m getting the SES light, but have some other Misc codes. Car seems less than quick off the line in normal driving. Car is new to me and was pretty poorly maintained. Only has 82k miles, but needed plugs and filters pretty bad when I got it. I just changed them, cleared all the codes, but these two codes keep coming back

    Codes 29F4 and 29F5

    What should I do first? O2 sensors? Which ones are more likely to need replacing? before or after cat?

    2011 328i N52 auto

    Thanks!

  2. #2
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    How many miles on your car? Catalysts have an 80,000 mile warranty.

    That said, if the O2 sensors are reading incorrectly, OR if you have crankcase ventilation problems, or other issues which are causing the engine to run less than perfectly, that will certainly cause catalyst efficiency codes.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  3. #3
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    82k miles. If it was the O2 sensors, which ones would be most likely to fail? Pre or post cat?

    thanks for the help.



    Quote Originally Posted by bmwdirtracer View Post
    How many miles on your car? Catalysts have an 80,000 mile warranty.

    That said, if the O2 sensors are reading incorrectly, OR if you have crankcase ventilation problems, or other issues which are causing the engine to run less than perfectly, that will certainly cause catalyst efficiency codes.

  4. #4
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    Do not erase codes. Take the car to a dealership, and advise them you've been told that the catalytic convertors have failed, and ask them if they will replace these under federal emissions warranty. Do not clear the codes, and do not mention a forum.

    Midland's not that far away. (I lived in Terlingua for 12 years)

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  5. #5
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    What maintenance have you done on the car? How old are the spark plugs? What repairs have you had to do?

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  6. #6
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    I changed the the spark plugs, air filter, cabin air filter, less than 200 miles ago. Bought a scanner, cleared the codes, drove it. After about 45 mins of driving SES light came back on. I planned on changing the O2 sensors, but didn’t want to waste the money if I was going to have to replace the cats. Car drives fine, but like I said, a mild stumble from a stop.


    Quote Originally Posted by bmwdirtracer View Post
    What maintenance have you done on the car? How old are the spark plugs? What repairs have you had to do?

  7. #7
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    Even if you end up having to replace the cats, it would be silly to put the old O2 sensors in the new exhaust. Cats don't just "die". Something kills them, like an engine that's running too rich or too lean, or dumping oil into the exhaust, etc. If the cats are dead, so are the sensors.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  8. #8
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    Sounds like you’re saying you think the cats are done, and I shouldn’t bother with changing the O2 sensors, right?

    Quote Originally Posted by bmwdirtracer View Post
    Even if you end up having to replace the cats, it would be silly to put the old O2 sensors in the new exhaust. Cats don't just "die". Something kills them, like an engine that's running too rich or too lean, or dumping oil into the exhaust, etc. If the cats are dead, so are the sensors.

  9. #9
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    No, that's exactly the opposite of what I said. Replace the sensors first, clear the codes, and see if they come back. If they do, you need cats also.

    But know that the cats didn't die because they were old. If they're dead, something killed them and you need to fix that something before replacing the cats, or you'll just kill the new ones.

    You might also want to have the latest software loaded into your car's computers, in case there's an update relating to this.
    Last edited by bmwdirtracer; 07-26-2018 at 07:30 PM.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  10. #10
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    Ok I understand. Should I replace all 4 sensors or are the 2 pre-cat sensors or the 2 post-cat sensors more likely to cause this problem?

    Quote Originally Posted by bmwdirtracer View Post
    No, that's exactly the opposite of what I said. Replace the sensors first, clear the codes, and see if they come back. If they do, you need cats also.

    But know that the cats didn't die because they were old. If they're dead, something killed them and you need to fix that something before replacing the cats, or you'll just kill the new ones.

    You might also want to have the latest software loaded into your car's computers, in case there's an update relating to this.

  11. #11
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    Well, that's a difficult question. The primary sensors certainly live in a more difficult environment...AND they contribute more to the fuel mixture decisions made by the computer. On the other hand, the secondary sensors are the ones which are sending the information that the catalysts are not doing their job, because they're measuring the efficiency of the cats.

    Personally, I think you'd be best served by having a little more hands-on professional diagnosis done by a BMW specialist shop. It's not normal for a car to be having catalyst efficiency codes at this mileage. Perhaps the engine's burning oil, or perhaps it's running too rich or too lean (which should set other codes), or maybe BMW's even got more recent software for your computers that will have a "fix" for this issue.

    Your oxygen sensors are very expensive - the catalysts even more so. I have to again recommend proper diagnosis of causative faults BEFORE throwing parts at it.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  12. #12
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    O2 sensors and cats are probably quite OK, since both banks are reporting the error simultaneously.

    I am having the same problem on an N52B25 in a 525xi (Europe model). So far, I have eliminated other error codes that might have been causing the cat errors, including Vanos solenoid exchange and both DISA valves renewed, new sparkplugs and airfilter.

    Due to excessive oil consumption, I even had a major engine overhaul done with new piston rings and crankcase ventilation and a total overhaul of the cylinder head and valves. It seemed to cure the oil consumption but had nothing to do with the cat error codes.

    “My” BMW expert mechanic has found the brake booster is leaking air. And that air - he explains - ends up in the intake via the crankcase ventilation. And the electronics cannot measure that air and thus it gives the wrong air / fuel mix, which in turn may be causing the cat error codes.

    And he is right that it leaks air: For about 20 seconds after I stop the engine, I can hear a hissing sound and after that there is no pressure left to assist me in applying the brakes. And if I push the brake pedal while stopping the engine, the hissing sound is delayed until I release the brake. I.e. the valve in the brake booster closest to the brake pedal is leaking air.

    I hope he is right about this vacuum leak causing the cat error codes. He also claims that failing cats on an N52 is not a common problem. But the error codes are. And they are usually caused by a fault in either the intake system or the fuel injection.

    I have ordered a new brake booster.

    JimmyJam83: What did you do to solve your problem?

  13. #13
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    Some body needs to do the correct diagnostics before changing any parts

  14. #14
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    New brake booster mounted. It made no change to the error codes. But the brake booster is now working as it should. So no money wasted, but still left with catalyzer errors.

    Next up is examining the internals of the cats with a camera.

  15. #15
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    You rebuilt your engine because of excessive oil consumption. All that oil went through the cats, which is very likely to have ruined them. Oil, coolant, rich mixtures or lean mixtures will all destroy catalysts very quickly.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  16. #16
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    That is absolutely correct. The camera revealed ruined catalyzers. They have now been replaced and the error codes are gone. Or at least there are no error codes after 600 km.

    I am just mad that when I bought the car, I asked BMW how much oil such and engine may consume. Their answer was one liter for every 1000 km. And at that time, the car “only” consumed a liter for every 3500 km. So I was left with no possibilities for complaining where I bought the car, even though I bought the thing with 3 months guarantee.

    After a couple of years and 40.000 km more, the oil consumption had worsened and was a liter for every 1500 or 2000 km. I.e. never as bad as BMW’s “specification” for what makes a bad engine. But obviously more than enough to destroy the catalyzers.

  17. #17
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    If the cat codes are efficiency faults then cats are done or you install this spark plug adaptors on the o2 sensors to pull the sensor out of the exhaust stream and the faults might not return. Of course the cats would still be bad but the light would be off.

  18. #18
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    Hi all sorry to be a pain
    I have a BMW 1 series 2009 116i which kept cutting out when driving happened once 6 month ago and then recently started again and jumping when driving. Long story short I took it to a garage who did a diagnosis and the codes were:

    2A26/Present - DME catalyst converter in stratified charge mode.
    29F4/Not present - DME catalyst converter Conversion
    23C1/Not present - Oxygen sensor emissions control.

    The garage said a new converter is needed which is fine ... estimated a few hundred pounds. I decided to save some money and fix it myself(the garage arent very reliable and I can't drive it far as its stuck on limp mode) however there are TWO catalyst converters on the car (manifold and the exhaust) the garage haven't told me which.

    I've search google/YouTube etc. Any ideas?

    Currently have a manny cat on hold at a party dealer so I have to get sorted soon! Any help or ideas would be really appreciated!

    Thanks in advance!!

  19. #19
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    Quote Originally Posted by Crpb1027 View Post
    Hi all sorry to be a pain
    I have a BMW 1 series 2009 116i which kept cutting out when driving happened once 6 month ago and then recently started again and jumping when driving. Long story short I took it to a garage who did a diagnosis and the codes were:

    2A26/Present - DME catalyst converter in stratified charge mode.
    29F4/Not present - DME catalyst converter Conversion
    23C1/Not present - Oxygen sensor emissions control.

    The garage said a new converter is needed which is fine ... estimated a few hundred pounds. I decided to save some money and fix it myself(the garage arent very reliable and I can't drive it far as its stuck on limp mode) however there are TWO catalyst converters on the car (manifold and the exhaust) the garage haven't told me which.

    I've search google/YouTube etc. Any ideas?

    Currently have a manny cat on hold at a party dealer so I have to get sorted soon! Any help or ideas would be really appreciated!

    Thanks in advance!!
    Hey i have the exact codes well 2 of them 2a26 and 29f4... i have changed the o2 sensors but it didnt work.. did you fix your if so which catalytic converter was it the manifold or rear one and did it work after replacing ?

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